SECTION II.. The Muscles.

THE MUSCLES.

THE MUSCLES.

LITERATURE.

Anonymous, Ueber das Schultergerüst der Schildkröten mit den daran sitzenden Muskeln. Isis, 1827. (Contains remarks on the shoulder-muscles of the frog.)

*Carus*, *C. G.* (1) Lehrbuch der vergleichenden Zootomie. 2nd Edit. Leipzig, 1834. (2) Erläuterungstafeln zur vergleichenden Anatomie. 1 Part. 1826. (Muscles of the Leg.)

*Chappuis*, Morphologische Stellung der kleinen hintern Kopfmuskeln. Zeit. f. Anat. u. Entwickl. 1876. Vol. II, pages 287–297.

*Cuvier*, Leçons d’anatomie comparée. Paris, 1835. Vols. I, II.

*Dugès*, Recherches anatomiques et physiologiques sur la déglutition dans les Reptiles. Ext. des Annales des Sciences naturelles. Paris, 1827.

*Dugès*, Leçons d’anatomie comparée. Paris, 1835.

*Duméril and Bibron*, Erpétologie générale ou Histoire complète des Reptiles. 1836.

*Führbringer*, Zur vergleichenden Anatomie d. Schultermuskeln. Jenaische Zeitschr. 1873. Vol. VII.

*Klein*, Beiträge zur Anatomie der ungeschwänzten Batrachier (Rana temporaria, L.): in Jahrshefte des Vereins für vaterländische Naturkunde in Würtemburg. 6 Jahrgang. 1850. Page 1.

*Kuhl*, Beiträge zur Zoologie der Rana esculenta: in Beitr. z. Zool. Frankfurt, a. M. 1820. Page 115.

*de Mann*, Vergelykende myologische en neurologische studien over Amphibien en Vogels. Acad. Proefschrift. 1873.

*de Mann*, Myologie comparée de l’extrémité post. chez les amphibiens. Niederl. arch. f. Zool. 1874. Vol. II.

*Marshall*, The Frog. London and Manchester. 2nd Edit. 1885. Pages 60–71.

*Martin St. Ange*, Annales des sciences naturelles. Vol. XXIV. 1831. Page 393.

*Meckel*, System der vergleichenden Anatomie. Halle, 1828. Vols. III and IV.

*Pfeiffer*, Zur Anatomie des Schultergürtels und der Schultermuskeln bei Säugethieren, Vögeln und Amphibien. Giessen, 1854.

*Rymer Jones*, Article ‘Reptiles’ in Todd’s Cyclop. of Anatomy and Physiology. 1847–1852. Vol. IV. Page 263.

*Stannius*, Handbuch der Anatomie der Wirbelthiere. Vol. II. Zootomie der Amphibien. Berlin, 1856.

*Wagner*, Icones Zootomicae. Leipzig, 1841.

*Wagner*, Lehrbuch der vergleichenden Anatomie. Leipzig, 1834–35.

*Zenker*, Batrachomyologia. Diss. Jena, 1825.

THE MUSCLES.

I. MUSCLES OF THE HEAD.

I. MUSCLES OF THE EYE.

*1.* M. rectus inferior (Fig. 48 ri′).

*Dugès*, post-orbito-sous-oculaire, n. 12.--*Zenker*, depressor oculi.

This muscle arises by a very thin, almost thread-like tendon from the parasphenoid, near the foramen opticum, and becomes rapidly broader; it lies beneath the tendon of the membrana nictitans and a part of the m. retractor bulbi: then runs forwards and outwards to be attached into the lower part of the circumference of the eyeball.

Eye muscles of Rana esculenta, from below.

On the right side (i. e. in the left eye) the lev. bulbi (l) is taken away; on the left side it is still present.

l M. levator bulbi. l.a M. lev. anguli scapulae oi M. obliquus inferior. os M. obliquus superior. p M. pterygoideus. r M. retractor bulbi. re M. rectus externus. 1 First cervical vertebra. ]

*2.* M. rectus externus (Fig. 48 re).

*Dugès*, post-orbito-ex-oculaire, n. 14.

Arises by a thin, thread-like tendon from the parasphenoid near the foramen opticum, internal to and a little behind the m. rectus inferior: it then passes obliquely outwards over the m. retractor bulbi and the tendon of the membrana nictitans, to be inserted into the outer and hinder part of the circumference of the eyeball.

*3.* M. rectus internus (Fig. 48 ri).

*Dugès*, post-orbito-in-oculaire, n. 13.

A long, thin muscle, which arises by a thread-like tendon from the parasphenoid at the inner and hinder angle of the orbit, passes along its inner wall, and is inserted into the antero-internal part of the circumference of the eyeball.

*4.* M. rectus superior (Fig. 49 rs.).

*Dugès*, post-orbito-sous-oculaire.

Arises by a slender tendon from the fronto-parietal bone, widens rapidly, and runs forwards and outwards to be inserted into the upper part of the circumference of the bulbus.

Eye-muscles of Rana esculenta, from above.

n Membrana nictitans. n′ Tendon of membrana nictitans. p M. pterygoideus. rs. M. rectus superior. t M. temporalis. ]

*5.* M. obliquus inferior (Fig. 48 oi).

*Dugès*, pré-sous-orbito-oculaire.

This muscle arises near the floor of the orbital cavity, at the inner and anterior angle, from the palatine bone by a thin and long tendon, runs under Harder’s gland outwards and backwards, and is inserted, almost at a right angle with the axis of the eye, into the anterior part of the circumference of the eyeball.

*6.* M. obliquus superior (Fig. 48 os).

*Dugès*, pré-sus-orbito-oculaire, n. 7.

The tendon of this small muscle arises from the inner end of the palatine bone, near the origin of the m. obliquus inferior, runs upwards, backwards, and outwards, and passes into a flat muscle, which rapidly becomes broader, and is inserted into the upper surface of the eyeball.

Eye-muscles of Rana esculenta, from below, the m. recti and obliqui have been removed.

n′ Tendon of membrana nictitans. r M. retractor bulbi, lower part. r′ Second part of same. ]

*7.* M. retractor bulbi (Figs. 48 r, 50 r, r′).

*Dugès*, orbito-post-oculaire or choanide, n. 10.--*Zenker*, m. opticus.

This muscle surrounds the optic nerve, and is situated within the cone formed by the four recti muscles; it consists of three portions, which take their broad and fleshy (the recti and obliqui arise by thin tendons) origins from the under surface of the parasphenoid. The first portion (Fig. 50 r) arises from the under surface of the parasphenoid, nearly as far as the middle line, is broad and fleshy, and covers, from below, the tendon of the rectus externus, then runs forwards and outwards. The second portion (r′), which lies over this and the tendon of the m. rectus externus, has also a broad and fleshy origin, but runs more directly forwards, slightly crossing the preceding. The third portion arises above the two others by a strong thin tendon from the parasphenoid: it runs almost in the direction of the m. rectus internus, but more directly forwards. The first two portions pass more to the upper surface of the eyeball, the third more to the under surface; consequently the whole muscle forms a sheath surrounding the eyeball. The fibres to the upper surface of the eyeball are inserted somewhat in front of the equator of the eyeball, those to the under surface somewhat behind it.

*8.* M. levator bulbi, Dugès (Figs. 48 l, 51 l, 52 l).

*Dugès*, fronto-pterygoidien, n. 9.--*Klein*, sustentator bulbi.

Transverse section through the skull and orbital cavities of Rana esculenta.

b Bulb of eye. c Skull cavity. g Mucous membrane. l M. levator bulbi. m Upper jaw. n Membrana nictitans. n′ Continuation of same to the lower eyelid. p Upper eyelid. ]

M. levator bulbi of Rana esculenta, seen from above; the eyeball which rests on it has been removed.

d.p M. depressor palpebrae inferioris. l M. levator bulbi. n Membrana nictitans. p M. pterygoideus. t M. temporalis. ]

There is no bony floor to the orbital cavity, and the oral and orbital cavities are only separated by soft tissues; these are:--the mucous membrane of the mouth, a thin fascia, and above this the muscle under consideration. The fibres of this muscle run from before and from the inner side obliquely backwards and outwards, below all the remaining muscles of the eye, with the exception of the origin of the m. retractor bulbi, and the tendons of the m. obliquus inferior, and the m. pterygoideus; they arise on the inner side from the upper and outer border of the fronto-parietal bone (Fig. 51), also from the transverse portion of the parasphenoid and pterygoid bones, anteriorly from the sphenethmoid and palatine bones; they run first downwards, then, in the direction indicated, underneath the eye; and are inserted externally by means of tendinous fibres into the superior border of the upper jaw.

*9.* From the foregoing muscle certain fibres pass to the lower eyelid, which may be regarded as a *depressor palpebrae inferioris* (Fig. 52 d.p).

Manz has described a muscle as depressor palpebrae inferioris which arises in the neighbourhood of the external angle of the eye, somewhat behind and below the lower border of the orbit, thence passes obliquely upwards to be inserted into the lower eyelid. This description is right as regards the insertion, but needs correction as regards the origin. The muscle is attached to the orbital border in so far that the tendinous expansion, into which the levator bulbi passes at its external border, is attached into the upper jaw; this bundle splits off from the upper surface of the levator bulbi at its middle, and runs outwards on the under surface of the eyeball to the hinder part of the lower eyelid.

Eye-muscles of Rana esculenta, from below, the m. recti and obliqui have been removed.

n′ Tendon of membrana nictitans. r M. retractor bulbi, lower part. r′ Second part of same. ]

*10.* Tendon of the membrana nictitans (Fig. 53 n′).

The pigmented free border of the nictitating membrane passes, at the inner and outer angles of the eye, into a tendon which passes for some distance through fibrous tissue, then descends to the under surface of the eyeball and joins that of the opposite side, so that the free border of the eyelid, together with this tendon, form a complete ring. The tendinous part of the ring, which is thin and thread-like, is found on the under surface of the eyeball, and lies under the m. retractor bulbi, and is bound to this muscle by connective tissue. Manz is right in saying that the two muscles described by Dugès as levatores palpebrae inferiores (orbito-palpebral anterieur and posterieur, n. 5 and 6) do not exist; as is also the suggestion that he has confounded the tendon of the nictitating membrane with these; this is clearly shown in the figure in Plate VI of Dugès. With regard to the *actions* of these eye-muscles, it is plain that the four straight and two oblique muscles rotate the eyeball about three axes, one the axis of the eye, one vertical, and the third passing from behind forwards and inwards. The m. retractor pulls the eyeball into the orbital cavity backwards and downwards, while the levator raises it.

There is less agreement about the movements of the eyelids, or rather of the lower eyelid, for the upper has no independent movements. Dugès (l. c.) says that the two muscles, which he considers to be levatores palpebrae inferiores, and which, according to him, are connected with the m. retractor bulbi, draw up the lid as it is being drawn backwards and downwards by the latter muscle. The depression of the lid on the relaxation of the retractor and projection of the eyeball is due simply to elasticity. Manz, on the contrary, has shown that the sinking of the eyeball by the contraction of the retractor must necessarily cause a rising of the nictitating membrane, as its tendons are attached to that muscle and so must follow its movements.

The depression of the lower lid occurs simultaneously with the raising of the eyeball by means of the m. levator bulbi, through the contraction of the m. depressor palpebrae inferioris, which proceeds from that muscle; this is easily understood, as they are but parts of the same muscle.

II. MUSCLES OF THE FACE.

*11.* M. intermaxillaris s. dilatator narium (Fig. 54 im).

*Dugès*, intermaxillaire, n. 1.--*Zenker*, intermaxillaris medius.

This small muscle lies in the space between the vertical processes of the two premaxillary bones, and consists of obliquely-crossing fibres arising from the one bone and inserted into the opposite one. It brings together the processes of the intermaxillary bones, so that their upper extremities approach each other. At the same time, the cartilaginous nasal coverings or wings (an) diverge and the nares expand; hence we may regard this muscle as corresponding to a dilatator narium.

Facial muscles of Rana esculenta.

an Cartilaginous nasal alae. i′ Vertical process of premaxillary bone. im M. intermaxillaris. ln M. lateralis narium. n Cartilaginous nose capsule. ]

*12.* M. lateralis narium (Ecker), (Fig. 54 ln).

*Zenker*, m. intermaxillaris lateralis.--*Klein*, m. nasalis inferior.--*Dugès*, sus-maxillo-pré-nasal, n. 2.

This small muscle occupies the space between the anterior portion of the maxillary bone and the ascending process of the premaxillary bone. It arises from the maxillary, and ascends obliquely forwards to be inserted into the outer border of the ascending process of the premaxillary bone. It is antagonistic to the foregoing.

A third muscle is described by Dugès as sus-maxillo-post-nasal, n. 3 (nasalis externus, Klein); according to him it passes from the proc. nasalis of the maxillary bone to the outer border of the nasal opening, which it widens. According to Klein (l. c., p. 9), this muscle in R. temporaria runs to the upper border of the maxillary bone beneath the lower eyelid, and is long and narrow. I have, however, never been able to find muscular fibre in this situation.

III. MUSCLES OF THE LOWER JAW.

Muscles of the back and shoulder.

c M. cucullaris. dm,dm M. depressor maxillae, arising from the fascia dorsalis. On the right side it is cut through and reflected. fd Fascia dorsalis. fd′ Same cut near the spinous processes. i M. infraspinatus. l.a M. levator anguli scapulae. ld M. latissimus dorsi. r M. retrahens scapulae. sc M. sternocleidomastoideus. ]

*13.* M. depressor maxillae inferioris, Carus, Zenker (Figs. 55, 56, 63 d.m.).

*Cuvier*, l. c., II, 141, digastricus.--*Dugès*, sus-occipitodorso-angulaire, 32.

This is a strong, triangular muscle, wide above, pointed below. It is placed between the head and the shoulder-blade. It arises in two portions; the greater, from the fascia dorsalis (fd), covers the scapula, and passes inwards and backwards over the muscles of the back; anteriorly it passes over the m. temporalis and is attached to the fronto-parietal and squamosal, being continued to the fascia of the upper eyelid. The second part is smaller, and arises by fleshy fibres from the postero-superior arm of the squamosal, and from the posterior and inferior border of the cartilaginous tympanic ring. The two parts unite and are inserted into the hinder angle of the lower jaw. Cuvier correctly considers that only the anterior portion corresponds to the digastricus, the posterior answering to the m. cervico-maxillaris of snakes. It draws the lower jaw down and opens the mouth.

*14.* M. temporalis (Figs. 49, 52, 56, 57 t).

*Cuvier*, m. temporalis, I, l. c., p. 138.--*Dugès*, sous-rupéo-temporo-coronoidien.

This muscle, together with the M. pterygoideus, occupies the space between the prootic and the eyeball; it arises by the greater part of its fibres from the upper surface of the prootic; it passes, narrowing, beneath the anterior arm of the squamosal, then over the pterygoid bone, between this and the maxillary and quadrato-jugal, receiving on the way other fibres which arise from the anterior border of the inferior arm of the squamosal and from the anterior circumference of the tympanic ring. The collected fibres end in a broad, flat tendon, which is inserted into the inner surface of the so-called proc. coronoideus.

Muscles of the lower jaw of Rana esculenta.

d M. deltoideus. dm M. depressor maxillae, its origin where covering the m. temporalis reflected at *. ld M. latissimus dorsi. m M. masseter. t M. temporalis, origin. t′ Lower portion of same. ]

*15.* M. pterygoideus (Figs. 49 p, 52, 57 pt).

*Cuvier*, m. temporalis, II, l. c.--*Zenker*, m. massetericus, l. c., p. 25.--*Dugès*, pré-rupéo-pterygo-maxillaire, 31.

This is partly covered by the foregoing, and lies between it and the eyeball. It arises at the inner wall of the orbit from the fronto-parietal, and from that portion of the prootic which may be regarded as the ala magna, above the m. retractor bulbi. The muscle is broad, and compressed from before backwards: it runs downwards covered by the m. temporalis, and soon passes into a long, thin tendon (Fig. 57 pt), which is inserted, behind the m. temporalis and immediately in front of the joint, into the inner surface of the lower jaw.

*16.* M. masseter (Figs. 56, 57 m).

*Dugès*, zygomato-maxillaire, n. 29.

Arises as a somewhat broad muscle from the horizontal process of the quadrato-jugal and is inserted into the outer side of the lower jaw, opposite the insertion of the m. temporalis.

Muscles of the lower jaw of Rana esculenta.

dm M. depressor maxillae cut through and reflected. la M. levator anguli scapulae. l.d. M. latiss. dorsi, cut through and reflected. m M. masseter. pt M. pterygoideus. s Scapula. s′ Suprascapula. s.c. M. sternocleidomastoideus. t t M. temporalis cut through and reflected. ]

*17.* M. submaxillaris (Figs. 58, 59, 61 sm, sm′).

*Cuvier*, m. mylo-hyoideus, l.c., II, 536.--*Zenker*, mylo-sternoideus, p. 25.--*Dugès*, sous-maxillaire, n. 15.

This muscle forms the floor of the mouth as does the mylo-hyoideus in man; it is, however, not inserted into the hyoid bone.

It arises--1. From the whole of the inner surface of the upper border of the lower jaw, except near the angle (Fig. 58 sm);

2. By a small portion (Figs. 58, 59, 61 sm′) near the skull, from the cartilaginous anterior cornu of the hyoid-bone which projects from the cartilaginous part of the prootic bone. This portion descends along the cornu to unite with the other portion. The two together form a membranous layer, the fibres of which run transversely and meet in a band of connective tissue along the middle line, forming a kind of linea alba. The sheath runs forwards to the most projecting part of the lower jaw superficially to the m. submentalis. Slightly in front of its posterior border the muscle is attached in its whole breadth to the skin of the throat by a fine lamella of connective tissue, which is not always complete. The posterior border of the muscle is attached to a fascia, which passes between the deeper muscles and is attached to these. It is known that this muscle plays an important part in the movements of respiration and swallowing; but its precise action has not yet been worked out.

*18.* M. submentalis (Fig. 59 smt).

*Cuvier*, transversus, l. c., p. 588.--*Dugès*, 4, sous-mentonnier.--*Zenker*, m. lingualis (incorrectly brought into connection with m. hyoglossus).

This small muscle lies in the anterior angle of the lower jaw between the dentary bones. It consists of transverse fibres which pass from one bone to the other. Below it is covered by the most anterior portion of the m. submaxillaris.

Muscles of the throat, chest, and abdomen of Rana esculenta.

sm M. submaxillaris. sm′ Hinder portion of same arising from the anterior cornu of the hyoid bone.

(For other references see page 68.) ]

Its action is to approximate the sides of the lower jaw: according to Dugès (l. c., p. 123), it assists in closing the nostrils, by drawing together the sides of the lower jaw and thus raising the premaxillae.

IV. MUSCLES OF THE HYOID BONE AND THE TONGUE.

*19.* M. geniohyoideus (Figs. 59 gh, 60 gh).

*Cuvier*, IV, 1, 536.--*Dugès*, n. 16.--*Zenker*, p. 30.--*M. St. Ange*, l. c., Pl. XXVI, f. 1, 13, p. 423.

Arises from the lower jaw in two portions, the one from near the middle line above the m. submentalis, the other more externally from the upper border of the lower jaw. The two parts unite to form a long, flat muscle, which lies on the ventral surface of the body of the hyoid bone, and divides posteriorly into two portions. One of these, the median (Figs. 59, 60 gh″), is inserted into the inner border of the posterior horn of the hyoid bone, and is here attached to a fascia which covers the m. hyoglossus from beneath. By the same fascia the muscles of opposite sides are connected in the space between the two posterior cornua. The lateral division (Figs. 59, 60 gh′) is attached to the posterior cartilaginous process of the hyoid bone.

Muscles of the hyoid bone and the tongue of Rana esculenta.

The m. submaxillaris has been removed close to its insertion.

cm′ Origin of the hinder portion of same from the hyoid bone. gh M. geniohyoideus. gh′ External portion of same. gh″ Internal portion of same. H Body of hyoid bone. H′ Anterior horn. hg M. hyoglossus. oh M. omohyoideus. ph Mm. petrohyoidei. sh M. sternohyoideus. sh′ External origin of same. sh″ Internal origin of same. sm M. submaxillaris. sm′ Origin of hinder portion of same. smt M. submentalis. ]

*20.* M. sternohyoideus (Figs. 59 60 sh).

*Cuvier*, IV, 1, 538 (pubio-hyoideus).--*Dugès*, n. 17, sterno-xipho-hyoidien.--*Zenker*, p. 30.

This muscle forms the cervical part of the m. rectus abdominis and is, in fact, a direct continuation of it. It arises by an inner portion (Fig. 59 sh″) from the upper surface of the inner extremity of the coracoid and from the xiphisternum, while the outer portion (sh′) is an immediate continuation of the m. rectus abdominis, which passes into this muscle at about the fifth inscriptio tendinea. The muscle passes forwards on the upper surface of the coracoid and of the clavicle, under the pericardium towards the hyoid bone; here the muscle, hitherto horizontal, suddenly becomes (compare Fig. 60) vertical, and passes between the two insertions of the m. geniohyoideus, and is inserted for a considerable length into the lower surface of the hyoid bone and the anterior extremity of the posterior cornu.

Muscles of the tongue and of the hyoid bone of Rana esculenta, from below.

gh M. geniohyoideus. gh′ External origin } gh″ Internal origin } of same. H Body of hyoid. H′ Anterior cornu. H″ Posterior cornu. hg M. hyoglossus. hg′ Hinder origin of same. oh M. omohyoideus. ph. 1, 2, 3, 4, first, second, third, and fourth m. petrohyoideus. sh M. sternohyoideus. ]

*21.* M. omohyoideus (Figs. 59, 60 oh).

*Cuvier*, l.c., p. 539.--*Dugès*, n. 18, interscapulo-hyoidien ou omohyoidien.-- *Zenker*, p. 31.--*M. St. Ange*, l.c.

Arises from the anterior border of the bony scapula, and is inserted into the outer part of the ventral surface of the body of the hyoid: it is partially covered by the m. sternohyoideus.

*22.* M. petrohyoideus anterior (Ecker), (Fig. 61 ph1).

*Dugès*, 10, rupéo-cérato-hyoidien.--*Zenker*, m. petro-ceraus? p. 30.-- *Klein*, basio-hyoideus, l.c., p. 71.

A thin, flat muscle, narrow above, but broadening rapidly below, which arising from the outer extremity of the prootic bone, partially surrounds the pharynx below, into which some of its fibres are inserted; it is attached to the ventral surface of the body of the hyoid bone, near the lateral notch. The chief action of this muscle appears to be that of a m. constrictor pharyngis.

*23, 24, 25.* Mm. petrohyoidei posteriores (Ecker), (Figs. 61 ph 2, 3, 4).

*Cuvier*, mm. stylohyoidei, l. c., p. 537.--*Dugès*, 20, 21, 22, masto-hyoideus (Fig. 4).--*Zenker*, petro-hyoideus superior and inferior.--*Klein*, stylo-hyoideus, l. c., p. 18.

These are three long, thin muscles, which lie nearly parallel to one another, and run from the prootic bone to the posterior cornu of the hyoid bone. All three arise, covered by the m. sternocleidomastoideus, from the lateral extremity of the prootic, pass round the pharynx and are attached, the m. petrohyoideus posterior primus (Fig. 61 ph 2) to the anterior extremity, the secundus (Fig. 61 ph 3) to the middle; and the tertius (Fig. 61 ph 4) to the hinder extremity of the posterior horn of the hyoid bone.

*26.* M. hyoglossus (Figs. 59, 60, 61 hg).

*Cuvier*, l. c., p. 588.--*Dugès*, 24, hyo-glosse.

Arises from the bony posterior extremity of the hinder process of the hyoid bone (hg′). The muscles of the two sides pass forwards and converge to the middle line, where they unite. The azygos muscle thus formed runs forwards on the ventral surface of the hyoid bone, between the mm. geniohyoidei, over the anterior border of the hyoid, and passes into the tongue, where it turns backwards and runs to the tip. (For action, see tongue.)

Muscles of the hyoid bone of Rana esculenta, seen from the right side and below.

H′ Anterior cornu. H″ Posterior cornu. hg M. hyoglossus. H H Body of hyoid bone. ph 1 M. petrohyoideus anterior. ph 2, 3, 4 Mm. petrohyoidei posteriores. sm M. submaxillaris. sm′ Hinder portion of same. ]

*27.* M. genioglossus.

*Cuvier*, l. c., p. 587.--*Meckel*, l. c., IV, 339.--*Dugès*, 23, genio-glosse.

Arises above the insertion of the m. geniohyoideus on either side near the middle line from the two anterior bones of the lower jaw. The two origins quickly unite to form a thick, very firm muscular belly, which in its course backwards rapidly thins, and is distributed by numerous bundles; decussating with the fibres of the m. hyoglossus at an acute angle, it runs on to the anterior extremity of the tongue.

II. MUSCLES OF THE TRUNK.

I. MUSCLES OF THE ABDOMEN.

In the formation of the abdominal wall the following muscles take part:--(1) m. rectus abdominis, (2) m. obliquus externus, (3) m. obliquus internus, (4) the portia abdominalis of the m. pectoralis. Above, the m. obliquus internus forms a kind of *diaphragm*, partially separating the abdominal from the thoracic cavity (p. 70).

*28.* M. rectus abdominis (Fig. 62 r).

*Dugès*, pubio-thoracique, n. 52.

These muscles, situated on either side of the middle line of the abdomen, are as a rule traversed by five notched inscriptiones tendineae. Each muscle arises, by a narrow, strong tendon, from the inferior border of the pubes, passes forwards, and quickly widening, divides at the second inscriptio tendinea (counting from behind) into two portions.

(a) The Outer portion (Fig. 62 r) runs into the portio abdominalis of the m. pectoralis, and forms the greater lateral division of that muscle.

(b) The Inner (r′) continues as the m. rectus abdominis and gradually narrows anteriorly. At the sternum some of the fibres (the median) are inserted into the dorsal surface of the cartilaginous plate of the xiphisternum, while the greater part of the muscle continues forwards over the coracoid to become the m. sternohyoideus at about the fifth inscriptio tendinea (p. 64).

*29.* M. obliquus externus (Fig. 63 oe, oe′).

*Zenker*, l. c., p. 31, m. obliquus.--*Dugès*, dorso-sous-abdominal, n. 54.

The m. obliquus externus arises from--

(a) The aponeurosis covering the long muscles of the back, and by this from the spinous processes. The anterior edge of the m. obliquus externus covers the posterior edge of the m. latissimus dorsi, which arises from the inferior, ventral surface of the aponeurosis. The aponeurosis also divides laterally into two parts, one of which, the posterior, passes into the obliquus externus, while the anterior forms the tendon of origin of the depressor maxillae inf. (dm) (compare Fig. 66).

(b) A second, narrow portion, portio omo-abdominalis (Fig. 63 oe′) (m. xipho-adscapulaire, Dugès, n. 62), arises from the posterior border of the scapula by a thin tendon, and becomes broader as it runs downwards and backwards, to join the anterior border of the other and larger portion.

Muscles of the chest, throat, and belly of Rana esculenta.

ch M. coraco-humeralis. d M. deltoideus. oi M. obliquus abdom. internus. oe M. obliq. abdom. externus. oe′ Scapular portion of same. oh M. omohyoideus. p′ Port. sternalis anterior of m. pectoralis. p″ Port. sternalis posterior of same. p‴ Port. abdominalis of same. r M. rectus abdominis. r′ Inner portion of same. sh M. sternohyoideus. sm M. submaxillaris. sm′ Hyoid origin of same. sr M. sternoradialis. ]

The whole muscle is attached by its most anterior fibres to the cartilage of the xiphisternum, the rest passing into an aponeurosis which, inseparably connected with the inscriptiones tendineae, traverses the lower surface of the m. rectus abdominalis to the linea alba.

Muscles of trunk of Rana esculenta, from the right side.

cd M. cutaneus femoris. d M. deltoideus. d.m. M. depressor maxillae. i M. infraspinatus. ld M. latiss. dorsi. oe M. obliquus abdom. externus. oe′ Scapular origin of same. ss M. subscapularis. t M. triceps brachii. ]

*30.* M. obliquus internus (and transversus), (Figs. 64, 65 oi).

*Dugès*, ileo-transverso-sous-sternal, p. 53.--*Zenker*, transversus, l. c., p. 31.--*Kuhl*, transversus, l. c., p. 116.

This muscle corresponds with the combined obliquus internus and transversus, and has therefore been described either as the one or the other, by various authors.

The fibres arise tendinously--

*a.* From the transverse processes of the vertebrae from the fourth backwards, and from the fascia covering the mm. intertransversarii.

*b.* From the iliac bone, by a strong tendon from its upper border, and by a few weaker fibres from its outer surface. The latter fibres are covered by the former, and these end posteriorly in a sharp concave border.

The muscular bundles diverge from these points, some running forwards, some backwards; the former are only partially covered by the portio omo-abdominalis of the m. obliquus externus (compare Figs. 62, 63), in front of the anterior edge of that muscle. The posterior border of the muscle is uncovered.

Second layer of abdominal muscles of Rana esculenta, from the right side and below. The m. obliquus externus and the right anterior extremity has been removed.

dm M. depressor maxillae. hg M. hyoglossus. ld M. latissimus dorsi and infraspinatus. oi M. obliquus internus. oi′ Insertion of third portion of same. oi″ Second portion inserted into the pharynx. pc Pericardium. ph^4. M. petrohyoideus quartus. r M. rectus abdominis. ss M. subscapularis. ]

The insertions of the muscle are very various, and as a consequence very various functions are accomplished by it.

*a.* The most anterior part of the muscle (Fig. 65 oi‴), the fibres of which run forwards, is attached--

1. Partly to the xiphisternum and the coracoid.

2. A second portion, viz. that arising from the transverse processes of the fourth vertebra (Fig. 64 oi″), surrounds the pharynx like a diaphragm (Fig. 65 oe), and is attached to its side as far as the dorsal aspect (Fig. 65 oi′). This portion is lightly separated from the following.

3. A third portion, placed behind the preceding, runs from the pharynx over the pericardium (Fig. 64 pc), and is attached to this nearly as far as the middle line (Figs. 64 oi′ and 65 oi″), resting on the sternum, the m. rectus and m. sterno-hyoideus. The lines of insertion of the muscles of opposite sides form an angle, open in front. In the thin borders of this portion the muscular bundles lie almost entirely in simple layers, and they are therefore well adapted for microscopical purposes.

*b.* The middle and posterior portions of the muscle pass downwards and slightly backwards, towards the outer border of the m. rectus; there they pass into a tendon which, for the most part, runs on the upper surface of the rectus to the linea alba.

II. MUSCLES OF THE BACK.

The muscles of the back are covered by a fascia, the *fascia dorsalis* (Fig. 66 fd), attached to the spinous processes of the vertebrae. Anteriorly, where it covers the m. temporalis, it is attached to the fronto-parietal and squamosal bones, posteriorly to the superior border of the iliac bones and the extremity of the urostyle. The posterior part, which covers the origins of the m. longissimus dorsi, of the m. coccygeo-iliacus, and of the coccygeo-lumbaris, is especially strong. From the anterior part several muscles arise laterally, viz. a portion of the m. obliquus abdominalis externus, of the m. latissimus dorsi, and of the m. depressor maxillae inferioris. In the uppermost layer, immediately covered by the fascia dorsalis, lie the m. cucullaris, the m. retrahens scapulae, the m. latissimus dorsi arising from the fascia itself, and the scapula with its muscles; then come the long muscles of the back; and in the third and deepest layer the short muscles of the back.

M. obliquus internus, showing its attachments superiorly.

h Xiphisternum. oe Oesophagus. oi M. obliquus internus. oi′ Fibres of m. obliq. int., which are inserted into the oesophagus. oi″ oi‴ Fibres of same, which are attached to coracoid and xiphisternum. p Pericardium. r M. rectus abdominis. ]

The individual muscles are as follows:--

A. LIMB MUSCLES OF THE BACK (for moving the shoulder-girdle and arm).

*31.* M. cucullaris (Fig. 66 c).

*Cuvier*, angularis.--*Dugès*, n. 38, sous-occipito adscapulaire.--*Zenker*, levator scapulae sublimis.

In order to see this muscle, it is necessary to separate the fascia dorsalis from the spines of the vertebrae and to turn it back with the m. depressor maxillae inf. arising from it. It is then seen to rise from the posterior surface of the exoccipital as far as the middle line; the muscles of the two sides run backwards, diverging each from the other, so as to form an angle, and are then attached on each side to the anterior superior angle of the suprascapula at its under surface and median border.

Cuvier considers this muscle as the analogue of the m. levator anguli scapulae. Dugès and Meckel consider it to be the anterior part of the m. cucullaris, the former thinking the posterior part of the muscle to be the m. rhomboideus. I cannot agree with these opinions, and I regard the muscle as simply representing the m. cucullaris of man (Ecker).

*32.* M. latissimus dorsi (Figs. 56, 66 ld).

*Dugès*, n. 66, lombo-huméral.--*Zenker*, depressor brachii.

This thin, triangular muscle arises from the ventral surface of the fascia dorsalis, and is posteriorly covered in part by the anterior border of the m. obliquus abdominis externus. The muscle becomes narrower towards the sides, and passes into a flat tendon, which blends with that of the m. infraspinatus, and is attached to the outer surface of the crista deltoidea of the humerus by a triangular expansion.

*33.* M. retrahens scapulae (Ecker), (Fig. 66 r).

*Dugès*, n. 59, lombo-adscapulaire.--*Klein*, m. rhomboideus, l. c., p. 26.--*Zenker*, omoplateus rectus? p. 37, l. c.--*Kuhl*, l. c., 124, retrahens rhomboideus.

Muscles of the back and shoulder-blade.

c M. cucullaris. dm M. depressor maxillae arising from the fascia dorsalis, cut through and reflected on the right side. fd Fascia dorsalis. fd′ Same cut through at the spines. i M. infraspinatus. l.a M. levator anguli scapulae. ld M. Latissimus dorsi. r M. retrahens scapulae. sc M. sternocleidomastoideus. ]

This flat, oblong muscle arises from the transverse process of the fourth vertebra, and is connected with the third tendinous inscription (counting from before) of the m. longiss. dorsi. Posteriorly its origin forms a convex border, whence it runs forwards and to the side; it is inserted into the ventral surface of the suprascapula, near its inner border. This muscle lies near the m. serratus or transv. scap. tertius (Fig. 68 ts″), and has an analogous position. It would, therefore, possibly be more correct to regard it also as a m. serratus. It arises from parts which represent ribs, and is inserted into the scapula. It has, at any rate, no analogy to the m. cucullaris, with which Dugès connects it, nor with the m. rhomboideus, which Klein holds it to be, as it does not arise from spinous processes.

B. LONG MUSCLES OF THE BACK.

*34.* M. extensor dorsi communis (Fig. 67 lg.d.).

*Dugès*, n. 33–40, masse des muscles surspinaux devisée en huit faisceaux principaux: 1. vertebro-sus-occipital, 2–5. transverso-spinaux, 6. transverso-coccyg., 7. sacro-coccygien, 8. ileo-coccygien. The muscles 1–7 form the lombo-costal, 8 the ischicoccyg., Cuv.--*Zenker*, m. sacrolumbaris.--*Klein*, longiss. dorsi, coccygeo-lumb., coccyg.-iliac.

This muscular mass is covered by the fascia dorsalis, the m. cucullaris and retrahens scapula, and the suprascapula: it corresponds with (1) the m. ileo-costalis and longissimus dorsi, dorsi and cervicis (Henle); (2) the semispinalis and spinalis (Henle).

The following separate portions may be made out:--

*35.* (1) M. longiss. dorsi (Fig. 67 lg.d.).

This muscle arises from the most anterior part of the urostyle, runs forwards near the middle line, separated from the muscle of the opposite side by the spinous processes of the vertebrae. The inner portion passes over the posterior spinous processes without being connected with them, as far as the fifth, it is then inserted into the succeeding spines as far as the exoccipital bone. The lateral portion runs outwards and forwards to be attached to the transverse processes and oblique processes of all the vertebrae, from the sixth forwards, while accessory muscular slips arise from the transverse processes and from the anterior spinous processes which, merging in the general muscle-mass, are inserted with this into the occiput.

The muscle is subdivided by a series of wavy, tendinous partitions (Fig. 67), which arise from the transverse processes, and traverse the muscle in planes, the upper surfaces of which are directed upwards and forwards. This arrangement of the muscle indicates its relation with the lateral trunk muscles of fish and fish-like amphibians.

*36.* (2) M. coccygeo-sacralis (Fig. 67 c.l.).

This muscle is partially covered by the preceding, it arises from the lateral surfaces of the anterior half of the urostyle; from this origin the fibres pass forwards and outwards to be inserted in two portions, the anterior set into the arch and the posterior set into the transverse process of the last vertebra. The former may be regarded as m. intercruralis, the latter as m. intertransversarius.

*37.* (3) M. coccygeo-iliacus (Fig. 67 c.i.).

This muscle arises from nearly the whole length of the lateral surface of the urostyle, the anterior portion being concealed by the preceding muscle. The fibres pass outwards and forwards to be inserted into the anterior two-thirds of the inner surface of the ilium.

Muscles of the back and pelvic girdle of Rana esculenta.

c.i. M. coccygeo-iliacus. c.l. M. coccygeo-sacralis. g.l. M. glutaeus. i MM. intertransversarii. i′ MM. intercrurales. i.c.i. M. intertransv. capitis inferior. i.c.s. M. intertr. cap. sup. il. M. ilio-lumbaris. lg.d. M. longissimus dorsi. o.i. M. obliq. internus. t M. temporalis. ]

*38.* M. ilio-lumbaris (Klein), (Fig. 67 il.).

*Dugès, n.* 51, transverso-iliaque.--*Cuvier*, *Zenker*, etc., quadr. lumborum.

Evidently represents the quadratus lumborum of human anatomy; it takes its origin from the anterior extremity of the ilium, and runs forwards to be inserted into the transverse processes of the vertebrae from the seventh to the fourth.

C. SHORT MUSCLES OF THE BACK.

*39.* M. intertransversarius capitis superior (Ecker), (Fig. 67 i.c.s.).

*Dugès*, n. 41, ex-occipito-transversaire sup.

A small muscle arising from the prootic: it lies above the levator anguli scapulae, and is inserted into the transverse process of the second vertebra.

*40.* M. intertransversarius capitis inferior (Fig. 67 i.c.i.).

*Dugès*, n. 42, ex-occipito-transv. inf.

This muscle lies on the ventral surface of the preceding one, but is easily separable from it; it arises from the angle of the prootic and is inserted, together with the preceding muscle, into the transverse process of the third vertebra. The n. vagus passes outwards between these two muscles.

*41.* MM. intertransversarii dorsi (Fig. 67 i).

*Dugès*, n. 43 to 50, intertransversaires.

Seven small muscles, placed between adjacent transverse processes of the vertebrae; from the second to the last, in continuity with the muscles last mentioned.

*42.* MM. intercrurales (Ecker), (Fig. 67 i′).

*Klein*, p. 29, interspinales, interobliqui.

Those muscular fibres found between the arches of adjacent vertebrae are so named. On account of the shortness of the spinous processes they can scarcely be named m. interspinales.

III. MUSCLES OF THE ANTERIOR EXTREMITY.

I. MUSCLES OF THE SHOULDER-GIRDLE.

A. DORSAL MUSCLES OF THE SHOULDER-BLADE.

(I.) Muscles arising from the head or trunk, and inserted into the scapulae, which they act upon primarily, and upon the shoulder-girdles secondarily.

Some of these muscles, such as m. cucullaris and retrahens, are situated on the back, and have already been described with the muscles of that region. Others are attached partly to the under-surfaces of the scapulae and are only visible from below; they are best seen in such a preparation as is shown in Fig. 68, made by cutting through the sternum in the middle line, and reflecting each half outwards.

(*a*) Muscles which arise from the skull.

*43.* M. levator anguli scapulae (Fig. 68 la).

*Dugès*, sous-occipito-adscapulaire, n. 60.--*Zenker*, protractor scapulae, Pl. I, Fig. 5.--*Cuvier*, Leçons I, p. 379, describes this muscle as part of the m. serratus anticus magnus.

A fairly strong muscle, which has a broad origin from the prootic and exoccipital bones as far as the foramen magnum, a few fibres are also attached to the lateral portions of the parasphenoid. The fibres run backwards and outwards, first in a frontal plane and then in a sagittal plane, to be inserted into the under surface of the suprascapula near the posterior border, where it encloses the hinder border of the m. interscapularis.

Its action is to draw the shoulders forwards and inwards, or the head downwards.

*44.* M. sternocleidomastoideus (Fig. 68 sc).

*Dugès*, scapulo-mastoidien, n. 65.--*Cuvier*, sterno-mastoidien.--*Zenker*, protractor scapulae, Pl. I, Fig. 5, 1.

A narrow muscle placed in front of and externally to the preceding muscle; its general direction resembles that of the m. levator ang. scap.

The fibres arise from the most external part of the prootic and from the hindermost part of the squamosal, under cover of the m. digastricus maxillae, and from the hinder portion of the cartilaginous tympanic ring. Covered by these muscles, it passes backwards and downwards to be inserted into the concavity of the anterior border of the scapula; externally to the origin of the deltoid.

The action of this muscle is to draw the shoulder forwards and towards the middle line, or to bend the head downwards.

*45.* M. protrahens scapulae (Fig. 68 ps).

*Dugès*, *Zenker*, protractor acromii, Pl. I, Fig. 5, 3.

This muscle lies to the outer side of the rectus capitis inferior: it arises from the prootic, and runs backwards and outwards upon the levator anguli scapulae, to be inserted into the scapula.

It pulls the scapula forwards.

(*b*) Muscles which arise from the vertebrae.

*46.* M. transverso-scapularis major (Ecker), (Fig. 68 ts).

*Dugès*, transverso-interscapulaire, n. 63.--*Cuvier*, l. c., p. 380, probably regarded as a portion of the serratus.--*Zenker*, Pl. I, Fig. 5, 3; depressor acromii, Pl. II, Fig. 3, 15.--*Klein*, depressor scapulae.

This muscle arises by tendon from the cartilage of the transverse process of the fourth vertebra and by a slip from the cartilage of the transverse process of the third vertebra. Diminishing in size, the muscle passes outwards, forwards, and upwards to be inserted into the posterior border of the scapula, opposite the insertion of the m. sternocleidomastoideus. It draws the shoulder inwards, backwards, and downwards.

*47.* M. transverso-scapularis minor (Ecker), (Fig. 68 ts′).

*Dugès*, transverso-adscapulaire, n. 61.--*Cuvier*, regarded as part of the serratus.--*Zenker*, Pl. I, Fig. 5, 7, detractor scapulae.

This is much shorter than the muscle just described; it arises under cover of the m. levator scapulae, from the transverse process of the third vertebra in front of the transverso-scapularis major; and runs outwards and forwards to be inserted into the ventral surface of the cartilage of the scapula. The action of the muscle is to draw the shoulder inwards, backwards, and outwards. Dugès regards this muscle as a portion of the serratus anticus magnus, the remainder of which he considers is to be found in the portio scapularis of the m. obliquus externus (xipho-adscapulaire, Dugès, n. 62).

Muscles of the shoulder, from below; the sternum has been cut through and the sides drawn apart.

d Deltoideus. is Interscapularis. it Intertransversarii. la Lev. anguli scapulae. ps Protrahens scapulae. sc Sternocleidomastoideus. ss Subscapularis. ts Transverso-scap. major. ts′ Transverso-scap. minor. ts″ Transverso-scap. tertius. ]

*48.* M. transverso-scapularis tertius s. serratus (Ecker), (Fig. 68 ts″).

This is larger than the muscle just described; arising by a broad and flat origin from the transverse processes of third and fourth vertebrae, it runs upwards and inwards to be inserted into the ventral surface of the cartilaginous scapula near its inner border. In position, course, and action the muscle most nearly represents the m. serratus anticus of human anatomy.

(II.) Muscles on the scapula, that is, arising from the scapula and inserted into the scapula or humerus.

(*a*) Muscles on the deeper surface.

*49.* M. interscapularis (Fig. 69 i.s.).

*Dugès*, interscapulaire, n. 64.

Muscles of right shoulder and upper arm. The coracoids (co) and the clavicles (cl) have been drawn apart after cutting through the sternum.

c.h. M. coraco-humeralis. cl Clavicle. c.o. Coracoid. d M. deltoideus. d′ Clavicular portion of m. deltoideus. i M. infraspinatus. i.s. M. interscapularis. l.a. M. levator anguli scapulae. l.d. M. latissimus dorsi. p′ Sternal portion of m. deltoideus. p″ Anterior sternal portion of the m. pectoralis. p‴ Posterior sternal portion of the m. pectoralis. s Scapula. s.r. M. sternoradialis. t.r. M. triceps brachii. ]

One end of this muscle is tendinous, and is attached to the outer extremity of the suprascapula; from this the muscle, becoming fleshy and narrower, runs towards the middle line to become attached to the ridge on the ventral surface of the scapula, from which the m. deltoideus and the m. subscapularis arise, and between which it passes. It approximates the scapula and suprascapula and lessens the angle between them.

*50.* M. subscapularis (Fig. 70 ss).

*Dugès*, sous-scapulo huméral, n. 72.

This muscle is situated on the upper or visceral surface of the scapula. It arises from a bony ridge found on the upper surface of the coracoid and of the proc. coracoideus of the scapula. The muscle runs outwards and is inserted, after widening, into the inner surface of the crista deltoidea of the humerus; it is antagonistic to the deltoid, and draws the raised arm backwards and towards the trunk.

Right shoulder, from below, arm strongly abducted.

cl Clavicle. co Coracoid. d Deltoideus. d′ Clavicular portion of deltoid. h Humerus. ss Subscapular muscle. ]

(*b*) Muscles on the superficial surface.

*51.* M. infraspinatus (Fig. 57, between ld and dm, Fig. 71 i).

*Dugès*, adscapulo-huméral, n. 67.

The m. infraspinatus represents the m. infraspinatus, teres major and minor of human anatomy. It is of triangular form, with the broad base directed inwards; it arises from the whole of the upper surface of the suprascapula except along the inner border which is formed of hyaline cartilage alone: from this origin the fibres converge outwards to a flat tendon which unites with that of the m. latissimus dorsi to be inserted into the crista deltoidea humeri, by means of a thin, triangular, tendinous expansion.

Muscles of the back and shoulder.

c M. cucullaris. dm M. depressor maxillae. fd Fascia dorsalis. fd′ Fascia dorsalis reflected. i M. infraspinatus. l.a M. levator anguli scapulae. ld M. latissimus dorsi. r M. retrahens scapulae. sc M. sternocleidomastoideus. ]

*General arrangement of the muscles of the shoulder-blade.*

The muscles attached to the scapula and suprascapula are:

1. Muscles of the back (m. cucullaris and m. retrahens scap.).

2. Muscles of the neck (m. omohyoideus).

3. Muscles of the abdomen (portio scapularis of the m. obliquus externus).

4. True shoulder muscles (m. levator anguli scapulae; m. sternocleidomastoideus; m. protrahens scapulae; mm. transverso-scapularis major, minor, and tertius s. serratus; m. interscapularis; m. subscapularis; and the long head of the m. triceps).

*From above* the following are visible: m. cucullaris, a portion of the m. subscapularis, and the transverso-scapularis maior.

*From below* (after cutting through and drawing aside the two halves of the sternum) may be seen: the omohyoideus, sternocleidomastoideus, levator anguli scapulae, protrahens scapulae, transverso-scapularis minor and tertius, interscapularis and subscapularis.

B. VENTRAL MUSCLES OF THE SHOULDER (PECTORAL MUSCLES)

These arise from the sternum or shoulder-girdle and are inserted either into the humerus or into the radio-ulnar.

*52.* M. pectoralis (Fig. 72).

This is placed on the ventral surface of the shoulder-girdle and consists of the following parts:

(α) Portio sternalis anterior (Ecker), (Figs. 72, 73 p′).

*Dugès*, clavi-huméral, n. 70 (port. clavic. du grand pectoral).

This is the anterior portion of the m. pectoralis, it arises from the sternum proper and the epicoracoids. Broad at the origin, it becomes narrower as it runs outwards into a tendon attached to the crista deltoidea humeri.

(β) Portio sternalis posterior (Ecker), (Figs. 72, 73 p″).

*Dugès*, sterno-huméral, n. 71 (port. sternal du grand pectoral).--*Klein*, humero-sternalis.

This muscle is placed immediately behind the portio sternalis anterior, it has a somewhat broad origin from the sternum and xiphisternum; the muscle runs outwards and slightly forwards to be inserted into the groove beside the crista deltoidea humeri. The tendon of the m. sterno-radialis passes between these two portions of the m. pectoralis.

(γ) Portio abdominalis (Figs. 72, 73 p‴).

*Dugès*, abdomino-huméral, n. 69 (port. costal du grand pectoral).--*Zenker*, brachio-abdominalis.--*Klein*, humero-abdominalis.

Muscles of the chest, throat, and belly of Rana esculenta.

ch M. coraco-humeralis. d M. deltoideus. oi M. obliquus abdom. internus. oe M. obliq. abdom. externus. oe′ Scapular portion of same. oh M. omohyoideus. p′ Port. sternalis anterior to m. pectoralis. p″ Port. sternalis posterior to same. p‴ Port. abdominalis of same. r M. rectus abdominis. r′ Inner portion of same. sh M. sternohyoideus. sm M. submaxillaris. sm′ Hyoid origin of same. sr M. sternoradialis. ]

This portion represents that part of m. pectoralis major of human anatomy which arises from the costal cartilages, and more particularly that part which is connected with the aponeurosis of the m. obliquus abdominis externus. The muscle arises (1) from the m. rectus abdominis (Fig. 72 r), that is, it forms a direct continuation of the outer portion of this muscle; (2) the inner, smaller part arises from the superficial surface of the aponeurosis of the m. obliquus abdominis. The muscle becomes narrower as it courses outwards and forwards, the outer fibres being longer and more oblique than the inner. The action of this muscle will necessarily vary according to the part or parts which are brought into action; speaking generally, the anterior extremities will be drawn downwards and towards each other.

*53.* M. coraco-humeralis (Dugès), (Figs. 72, 73 c.h.).

*Dugès*, n. 72.--*Klein*, adductor humeri.

A long, narrow muscle, lying upon the posterior border of the coracoid and the lowest part of the m. subscapularis. By its position it corresponds most nearly with the m. pectoralis minor, although its insertion does not. It has a narrow origin from the coracoid near the sternum, whence it courses outwards, under cover of the port. sternalis anterior and posterior of the m. pectoralis, to be inserted into the middle of the humerus between the deltoid and internal head of the triceps. It draws the limb towards the trunk.

*54.* M. sternoradialis (Cuvier), (Figs. 72, 73 s.r.).

*Dugès*, pré-sterno-clavi-radial, n. 74.

This muscle evidently represents the biceps of man, it lies in front of the portio sternalis anterior of the m. pectoralis, its hinder border being under cover of the latter muscle. It takes origin from the episternum, omosternum, and the epicoracoid; from this broad origin the fibres converge while coursing backwards and outwards to be attached to a strong tendon. This tendon plays in a groove along the crista deltoidea, and is held in position by tendinous bands arising from the insertion of the m. pectoralis; it then pierces the lower portion of the muscular belly of the deltoid, and is inserted into the anterior extremity of the radial side of the radio-ulnar. The muscle is a powerful flexor of the forearm.

*55.* M. deltoideus (Figs. 70, 72, 73 d).

*Dugès*, pré-sterno-scapulo-huméral, n. 68.

It is placed in front of and external to the m. sternoradialis, and represents both the m. deltoideus and supraspinatus of man. The muscle has two points of origin:--

(*a*) Portio scapularis, the larger, external portion is attached to the outer end of the clavicle, and to the anterior process of the precoracoid, but it arises chiefly from the dorsal surface of the scapula (from the same ridge as the m. subscapularis), and lastly from the anterior border and ventral surface of the scapula. The fibres pass outwards over the shoulder-joint.

Muscle of right shoulder and upper arm. The coracoids (c.o.) and the clavicles (cl) have been drawn asunder after cutting through the sternum.

c.h. M. coraco-humeralis. cl Clavicle. c.o. Coracoid. d M. deltoideus. d′ Clavicular portion of m. deltoideus. i M. infraspinatus. i.s. M. interscapularis. l.a. M. levator anguli scapulae. l.d. M. latissimus dorsi. p′ Sternal portion of m. deltoideus. p″ Anterior sternal portion of the m. pectoralis. p‴ Posterior sternal portion of the m. pectoralis. s Scapula. s.r. M. sternoradialis. t.r. M. triceps brachii. ]

(*b*) Pars clavicularis (musc. cleido-humeralis, Klein) arises from the inner extremity of the clavicle and from the omosternum and joins the portio scapularis.

The muscle is inserted into the humerus, the under part of the portio scapularis being attached to the upper portion of the crista deltoidea; the outer fibres of this part, together with those of the pars clavicularis, are attached to the extremity of the crista deltoidea and to the inner surface of the humerus as far as the distal extremity; just before its insertion the muscle is pierced by the tendon of the m. sternoradialis. The deltoid draws the limb forwards.

II. MUSCLES OF THE FORE-LIMB.

A. MUSCLES OF THE ARM.

M. sternoradialis (biceps). See page 82.

*56.* M. triceps brachii (Fig. 73 t.r.).

*Dugès*, scapulo-huméro-olecranien, n. 75.--*Capes*, *Zenker*, m. anconaeus.

This muscle lies on the upper or dorsal surface of the arm, and has relations similar to those of the corresponding muscle in man. The long head arises from the posterior border of the scapula at the upper border of the glenoid cavity, and is here attached to the capsule of the joint; the inner head arises from the upper and inner surfaces of the anterior half of the humerus as far as the extremity; the outer head arises from the outer surface of the humerus. Additional fibres, which may be regarded as a fourth origin (m. subanconaeus), arise from the upper surface of the hinder half of the humerus. The fibres from these several origins unite to form a strong muscle, which covers the upper, inner, and outer surfaces of the bone, and then passes into a tendon. This tendon is attached to the capsule of the elbow-joint and inserted into the proximal extremity of the radio-ulnar. A cartilage, representing the olecranon, is found in the capsule at the point of attachment of the tendon.

B. MUSCLES OF THE FOREARM.

(I.) Muscles of the flexor surface.

The muscles of this surface are arranged in two groups, so as to form, at the elbow-joint, a triangular depression (plica cubiti), into which the tendon of the m. sternoradialis sinks.

A. Muscles of the Inner Group.

*57.* M. flexor carpi I s. radialis (Fig. 74 Fc).

*Dugès*, sous-huméro-carpien, n. 83.

This represents either the flexor carpi radialis longior or radialis brevior of man; it has a broad origin from the inner border of the humerus above the epicondylus medialis. It becomes narrower as it passes downwards to be inserted by a tendon into the os semilunare and naviculare. The muscle is much stronger in males than in females, and the crest from which it takes origin is correspondingly larger in the former sex (p. 42). Tendinous fibres connect it with the following muscles:--

*58.* M. flexor carpi II s. ulnaris (Fig. 74 Fc′).

*Dugès*, epitrochlo-carpien, n. 84.

This muscle represents the flexor carpi ulnaris or ulnaris anterior, and is close to the inner side of the foregoing. It arises from the epicondylus medialis, being connected by fibres with the flexor digitorum communis, and is inserted into the os naviculare.

Muscles of the right arm of Rana esculenta.

ed M. extens. digitorum communis. ei M. abductor digiti II longus. Fa′ M. flexor antibrachii lateralis superficialis. Fc M. flexor carpi radial. Fc′ M. flexor carpi ulnar. Fd M. flexor digitorum communis. sr Tendon of the M. sternoradialis. ]

*59.* M. flexor digitorum communis (Figs. 75, 76, 77 Fd).

*Dugès*, epitrochlo-sous-phalangettien, n. 118.

This muscle lies most internally, and corresponds to the m. flexor digitorum sublimis of man. It arises in common with the foregoing muscle from the epicondylus medialis, and runs downwards to the palm of the hand. At its entrance into this it diminishes and passes into the flat aponeurosis palmaris. (See hand, B.)

*60.* M. flexor antibrachii medialis (Ecker), (Fig. 75 Fa).

*Dugès*, epitrochlo-sous-radial, n. 79. (Frequently described as the pronator rotundus, a description which cannot be retained, as the implied movement does not occur in the frog.--Ecker.)

This muscle lies deeply on the inner side of the forearm, covered by the flexores carpi; it arises tendinously from the epicondylus medialis and is inserted into the inner surface of the radial side of the radio-ulnar as far as the inferior articular extremity.

*61.* M. flexor antibrachii lateralis superficialis (Ecker), (Figs. 74, 75 Fa′).

*Dugès*, premier ex-huméro-radial, n. 76. (Usually described as supinator longus, this, for reasons similar to those in the case of m. flexor antibrachii medialis, cannot be retained.)

The situation of this muscle corresponds with that of the supinator longus of man; it lies to the outer side of the tendon of the m. sternoradialis, and arises by two heads, the one, above from the outer edge of the humerus, the other deeper from the epicondylus lateralis. They unite and pass into a tendon which, running over the lower articular extremity of the radio-ulnar, is partly attached to the carpus and partly connected with the tendon of the m. extensor digiti II proprius longus. From its position and insertion, this muscle evidently flexes the forearm and extends the hand.

Muscles of the right arm of Rana esculenta, deep layer.

ed Extensor digit. communis. Fa Flexor antibrachii medialis. Fa′ Flexor antibrachii lat. superficialis. Fa″ Flexor antibr. lat. profundus. Fc Flexor carpi radialis. Fc′ Flexor carpi ulnaris. Fd Flexor digitorum communis. ]

*62.* M. flexor antibrachii lateralis profundus (Ecker), (Fig. 75 Fa″).

*Dugès*, epicondylo-sus-radial, n. 78.--*Klein*, flexor antibrachii. (Supinat. brevis autt.)

This muscle arises under cover of the foregoing, from the epicondylus lateralis of the outer surface of the humerus, it becomes broader and is inserted into the whole length of the lower (volar) ridge of the radio-ulnar. It is a powerful flexor of the forearm.

(II.) Muscles of the extensor surface.

*63.* M. extensor digitorum communis longus (Fig. 75 ed).

*Dugès*, huméro-sus-digital, n. 95.

This muscle lies on the outer border of the forearm; it arises in common with the short head of the flexor antibr. lateralis superficialis from the epicondylus lateralis, and from the surface above it; it runs downwards along the outer side of the forearm, in order to pass into an aponeurosis on the back of the hand, which expands upon the third, fourth, and fifth fingers, and ends between them in a free concave border. This aponeurotic expansion is connected with the tendons of the extensor brevis digitorum.

*63*.* M. abductor digiti II (i. e. pollicis) longus (Fig. 74 ei).

**Dugès*, cubito-métacarpien, n. 87.

This muscle lies between the foregoing and the flexor antibrachii lateralis superficialis, and appears superficially in the interval between them. It arises from the lateral surface of the radio-ulnar, and runs obliquely over the m. flexor antibrachii lateralis profundus and the hinder extremity of the radio-ulnar towards the second finger into the metacarpal bones of which it is inserted.

*64.* M. extensor carpi ulnaris s. ulnaris post. (Fig. 76 ec).

*Dugès*, epicondylo-sous-carpien, n. 85.--*Klein*, abductor carpi internus.

This muscle has a somewhat narrow origin from the epicondylus lateralis; during its course through the forearm, where it lies between the mm. anconaei on the one side and the extensor digitorum communi on the other, it becomes broader and is inserted into the outer surface of the carpus in the following manner. By one tendinous slip it is attached to the palmar border of the os pyramidale, by a second slip to the outer border of the os capitato-hamatum. This latter slip is usually connected in its dorsal portion with the extensor digitorum communis brevis.

Muscles of forearm of Rana esculenta, dorsal view.

aa M. anconaei. ec M. extens. digit. communis. Fd M. flex. digit. ]

*65, 66.* M. anconaei s. extensores antibrachii (Fig. 76 aa).

*Dugès*, epicondylo-cubital and epitrochlo-cubital, n. 80, 81.

Both these muscles lie on the extensor side of the forearm; they spring, the one from the epicondylus lateralis, the other from the epicondylus medialis; converging, they run downwards, enclose the olecranon, and are inserted into the upper (dorsal) border of the ulna, each forming a penniform muscle. They are extensors of the forearm and assist the m. triceps.

C. MUSCLES OF THE HAND.

(I.) Muscles on the palmar surface.

(1) Muscles common to all the digits.

*67.* M. flexor digitorum communis and m. palmaris brevis (Fig. 77 fd, pb).

The origin and course of this muscle has been described above. At its entrance into the palm it suddenly diminishes in size and passes into a triangular aponeurosis, aponeurosis palmaris. Into the outer border of this aponeurosis is inserted the m. palmaris brevis (Fig. 77 pb); this latter muscle arises from the posterior or ulnar border of the lower extremity of the radio-ulnar below the insertion of the mm. anconaei, and runs obliquely downwards to this insertion.

From the lower free border of the aponeurosis a number of muscles arise which will be described with the rest of the digital muscles.

(2) Muscles of the rudimentary thumb.

*68.* M. abductor pollicis (Figs. 77, 78 ap).

*Dugès*, cubito-pollicien, n. 100.

This short muscle arises from the upper border of the lower extremity of the radio-ulnar, passes transversely outwards, and is then inserted into the anterior border of the rudimentary thumb.

*69.* M. adductor pollicis (Figs. 77, 78 ad.p).

*Dugès*, sous-carpo-pollicien, n. 101.

This lies more superficially than the last, it arises from the palmar surface of the os capitato-hamatum, and is inserted together with the abductor pollicis into the thumb. Several fibres of the extens. dig. II brevis are also inserted into the thumb. As this member is completely covered with skin, the motions of which it is capable are very limited.

(3) Muscles of the second finger, which serves the purposes of a thumb.

*70.* M. flexor digiti II longus s. sublimis (Fig. 77 f2).

*Dugès*, sous-carpo-phalangettien de l’index, n. 133.

Muscles of hand of Rana esculenta, volar surface, larger than nature.

A Aponeurosis palmaris. ab5 M. abductor dig. V primus. ab5′ M. abductor dig. secundus. ac MM. anconaei. adp M. adductor pollicis. ap M. abductor pollicis. ec M. extensor digitorum communis. e5 M. extens. dig. commun. brevis. f2 M. flexor dig. II longus. f3 M. flexor dig. III longus. f4 M. flexor dig. IV longus. f5 M. flexor dig. V longus. fb2 M. flexor dig. II brevis. fb3 and fb3′ MM. flexores dig. III breves. fb4 and fb4′ MM. flexores dig. IV breves. fb5 M. flexor dig. V primus. fd M. flexor digitorum communis. o M. opponens. pb M. palmaris brevis. I First finger, rudimentary thumb. II Second finger, functions as thumb. III-V Third to fifth fingers. ]

This is a flat muscle, which arises for the most part by fleshy fibres from the hinder free border of the aponeurosis palmaris, also by a smaller part from the palmar surface of the os capitato-hamatum. It quickly passes into a thin long tendon which is inserted into the terminal phalanx of the thumb (second finger).

Second layer of muscles on volar surface of hand of Rana esculenta, larger than nature.

ab5 M. abductor dig. V primus. ab5′ M. abductor dig. V secundus. ad2 M. adductor dig. II. ad.p M. adductor pollicis. ap M. abductor pollicis. ec M. extensor carpi. fb2 M. flexor dig. II brevis. fb2′ M. flexor dig. II tertius. fp MM. flexores proprii phalangum. i3 } i4 } MM. interossei volares. i4′} i5 } o M. opponens dig. II. o′ M. opponens dig. V. tt ′ MM. transversi metacarpi. I-V as in Fig. 77. ]

*71.* M. flexor digiti II brevis s. profundus (Fig. 77 fb2).

*Dugès*, sous-carpo-phalangien de l’index, n. 102.

This flat muscle, covered by the preceding, has a tendinous origin from the palmar surface of the os capitato-hamatum, together with one head of the flexor sublimis, and is inserted into the basal phalanx.

*72.* M. flexor digiti II tertius (Fig. 78 fb2′).

*Dugès*, tendini-phalangien de l’index, n. 103.

A small, thin muscle which arises close to the foregoing from the os capitato-hamatum, and is inserted into the basal phalanx (see below, m. interosseus volaris I).

*73.* M. adductor digiti II (Fig. 78 ad2).

*Dugès*, métacarpo-métacarpien de l’index, n. 90.

This muscle represents the adductor pollicis of man; it arises from the base of the third os metacarpal and is inserted into the metacarpal of the second finger, which latter it draws towards the third finger.

*74.* M. opponens digiti II (Figs. 77 and 78 o).

*Dugès*, sous-carpo-métacarpien de l’index, n. 90.

This muscle represents the muscle of like name in man. It arises from the palmar process of the os capitato-hamatum by a narrow tendon and passes into a broad, flat muscle, which is inserted into the under surface and outer border of the metacarpal of the second finger throughout its length. It has, undoubtedly, the same action as the corresponding muscle in man.

(4) Muscles of the third finger.

*75.* M. flexor digiti III longus s. sublimis (Fig. 77 f3).

The smaller portion of this muscle arises from the free border of the aponeurosis palmaris, the chief portion, together with the flexor brevis, from the palmar surface of the os capitato-hamatum. The two portions pass into one long tendon, which is inserted into the last phalanx.

*76, 77.* MM. flexores digiti III breves s. profundi I, II (Fig. 77 fb3 and fb3′).

*Dugès*, tendini-phalangiens du medius, n. 104, 105.

These two muscles arise in part from the free border of the aponeurosis palmaris, in part from the volar surface of the os capitato-hamatum, and pass backwards on either side of the muscle last described, to be inserted into the basal phalanx. Dugès regards these as analogues of the mm. lumbricales.

*78.* M. flexor metacarpi dig. III.

This is a somewhat strong muscle, which arises by fleshy fibres from the palmar surface of the os capitato-hamatum, and is inserted into the palmar surface of the metacarpal bone.

(5) Muscles of the fourth finger.

*79.* M. flexor digiti IV longus s. sublimis (Fig. 77 f4).

It arises at the free border of the aponeurosis palmaris, and is inserted into the terminal phalanx by a thin tendon.

*80, 81.* MM. flexores digiti IV breves s. profundi I, II (Fig. 77 fb4 and fb4′).

*Dugès*, tendini-phalangiens de l’annulaire, n. 108, 109.

Dugès regards these also as analogues of the m. lumbricales; they arise on either side of the foregoing muscle from the free border of the aponeurosis palmaris, and are inserted by tendons into the basal phalanx.

*82.* M. flexor proprius phalangum dig. IV (Fig. 78 fp).

*Dugès*, phalango-phalangien, n. 115.

A small muscle which arises by two slips from the palmar surface of the basal phalanx, and is inserted into the base of the middle phalanx.

*83.* M. flexor metacarpi dig. IV (Fig. 78 i4).

This somewhat strong muscle arises from the os capitato-hamatum, and is inserted into the palmar surface of the metacarpal bone.

(6) Muscles of the fifth finger.

*84.* M. flexor dig. V longus s. sublimis (Fig. 77 f5).

This corresponds exactly with the corresponding muscle of the fourth finger.

*85.* M. flexor dig. V brevis (Fig. 77 fb5).

This muscle arises from the free border of the aponeurosis and is inserted into the basal phalanx.

*86.* M. flexor proprius phalangum dig. V (Fig. 78 fp).

*Dugès*, phalango-phalangien, n. 17.

It corresponds exactly with the corresponding muscle of the fourth finger.

*87.* M. opponens dig. V (Fig. 78 o′).

*Dugès*, deuxième sous-carpo-métacarpien du digitule, n. 92.

This muscle has a narrow origin from the palmar surface of the os capitato-hamatum, it widens and is inserted into the outer border of the metacarpal of the small finger. It draws this finger towards the thumb.

*88.* M. abductor dig. V primus (Figs. 77 and 78 ab5).

*Dugès*, sous-pyro-pré-métacarpien du digitule, n. 93.

This muscle arises from the palmar border and the outer surface of the os pyramidale, and is inserted into the basal phalanx by a thin tendon.

*89.* M. abductor dig. V secundus (Figs. 77 and 78 ab5′).

*Dugès*, sous-pyro-post-métacarpien du digitule, n. 94.

It arises from the posterior part of the os pyramidale, is short, and is inserted into the outer side of the metacarpal.

(II.) Muscles on the dorsal surface.

M. extensor digitorum communis longus (Figs. 75 ed and 77 ec).

*90.* M. extensor digitorum communis brevis (Fig. 79 e3, e4, e5).

*Dugès*, sous-pyro-phalangettien du III, IV, V, n. 124, 128, 131.

Covered by the foregoing, this muscle arises from the os pyramidale in conjunction with the extensor pollicis and from the os capitato-hamatum. The part destined for the third finger, together with that for the fourth, arises from the os pyramidale, passes obliquely backwards into a tendon which runs along the inner side of the corresponding finger to be inserted into the last phalanx. That for the fifth finger arises from the inner projection of os capitato-hamatum being here attached to the insertion of the m. extensor carpi ulnaris, and is inserted in a similar manner into the terminal phalanx of the fifth finger.

*91.* M. abductor digiti II (i.e. pollicis) longus (Figs. 74 ei and 79 ab.2).

For the origin and course of this muscle in the forearm see No. 63. The muscle passes obliquely over the wrist-joint from the little finger towards the inner side and from before backwards, it is inserted into the metacarpal of the second finger (thumb). The place of insertion of this muscle into the metacarpal (compare p. 47) is, in the males, developed into a ridge and process, the muscle itself is enlarged during the breeding season. This muscle abducts the thumb and by this means presses upon the chest of the female when clinging to her.

*92.* M. extensor digiti II proprius longus (Fig. 79 e2, e2′).

*Dugès*, cubito-radio-sous-phalangien de l’index, n. 96.

Muscles of hand of Rana esculenta. Dorsal view, twice natural size.

ab.2. M. abductor dig. II longus. ab.2′ M. abductor dig. II brevis. ad.2 M. adductor dig. II. e2 } e2′ } M. extensor dig. II longus. e3 } e4 } M. extensor digitorum communis brevis. e5 } eb2 M. extensor dig. II proprius brevis. ec M. extensor carpi ulnaris. fa M. flexor antibr. lat. superficial. i′3 } i′4 } MM. interossei. i′5 } II-V as in Fig. 77. ]

This muscle lies obliquely on the back of the hand, parallel with the m. abductor digiti II. It arises by two heads, one from the tendon of the flexor antibr. lat. superf. (n. 60) upon the hinder extremity of the radio-ulnar. This tendon conceals the hinder end of this bone by means of a patella-like thickening, and sends forth three tendinous prolongations; of these, the one is attached to the ulnar border of the radio-ulnar, the second to the os naviculare, while the third constitutes that portion of the m. extens. dig. II proprius long. which is under consideration. The second head arises from the os pyramidale in connection with the extensor digitorum communis brevis (n. 90). The heads unite to form a long muscle, which runs obliquely towards the second finger, passes into a tendon, which, after forming connections by some muscular fibres with the metacarpal, is inserted into the terminal phalanx.

*93.* M. extensor dig. II proprius brevis (Fig. 79 eb2).

*Dugès*, sus-luno-phalangettien de l’index, n. 120.

This muscle lies between the preceding muscle and the abductor dig. II longus. It arises from the os naviculare, and also includes some fibres which arise from the second metacarpal. The tendon runs along the radial side and is inserted along with the last muscle into the terminal phalanx.

*94.* M. abductor dig. II brevis (Fig. 79 ab.2′).

*Dugès*, sus-luno-métacarpien de l’index, n. 88.

This represents the abduct. pollic. brevis of man, lies on the outer side of the hand, arises from the os naviculare, and is inserted into the second metacarpal.

*95.* M. extensor dig. III proprius.

*Dugès*, sus-luno-phalangettien du médius, n. 122.

This muscle has two heads of origin, from the os naviculare and lunatum. These form one muscular belly, which rapidly diminishes and passes into a tendon; this, after receiving a few muscular fibres from the second metacarpal, runs to the outer part of the dorsal surface of this finger as far as the terminal phalanx, where it is inserted.

*96.* M. extensor dig. IV proprius.

*Dugès*, sus-pyro-phalangettien de l’annulaire, n. 128.

By a somewhat broad base, this muscle arises from the os naviculare and lunatum. The tendon receives fibres from the fourth metacarpal and runs on the outer half of the dorsal surface of this finger as far as the middle phalanx, where it is inserted.

(III.) MM. interossei.

*97, 98.* [*a.*] MM. transversi metacarpi (Ecker), (Fig. 78 t, t′, ad2).

These lie transversely between the metacarpals. There are three; the first has been already described as m. adductor digiti II (n. 73); the second is stretched between the third and fourth metacarpals, and the third between those of the fourth and fifth fingers.

*99, 100, 101.* [*b.*] MM. interossei volares.

One may regard as such, four long, thin muscles, which take origin near one another on the palmar surface of the carpal bones, and diverge from this towards the second and fifth fingers.

1. The first of these muscles (Fig. 78 fb2′) has already been described above as the m. flexor digiti II tertius (n. 72).

2. The second (Fig. 78 i3) passes from the origin already described to the palmar surface of the basal phalanx of the third finger.

3. The third (Fig. 78 i4) runs, in like manner, to the fourth finger.

4. The fifth (Fig. 78 i5) to the fifth finger.

*102* to *108*. MM. interossei dorsales.

These arise in common from the metacarpals, and are inserted into the basal phalanx of the corresponding surface on the finger.

1. The third finger has two, one to the radial side (Fig. 79 i′3), one to the ulnar side.

2. The fourth finger has three, the third (Fig. 79 i′4) arises from the carpus, and perhaps ought rather to be regarded as an extensor.

3. The fifth finger has two.

IV. MUSCLES OF THE HINDER LIMB.

I. MUSCLES OF THE THIGH.

General arrangement (Figs. 80, 81).

*a.* The m. triceps femoris forms the outer border of the thigh, and extends on to both the dorsal and ventral surfaces. The outer border therefore corresponds with the anterior surface of the thigh of man, in consequence of the thigh in the frog being normally rotated outwards.

*b.* The m. vastus internus (v.i.) and a portion of the adductor longus (ad′), the sartorius (s), a portion of the adductor magnus (ad‴), and the rectus internus major (r.i′) are found on the inner surface of the thigh.

*c.* The rectus internus minor (r.i″) forms the inner border.

*d.* On the dorsal surface are to be seen, nearest the trunk, the glutaeus (gl), on the outer border the vastus externus (v.e.), the pyriformis and biceps (p and b), then the semimembranosus (sm), and lastly the rectus internus minor (ri″).

*e.* By reflecting the rectus internus major (compare Fig. 82) there are exposed to view: the semitendinosus (st), the whole length of the adductor longus, magnus (ad′ and ad‴), and brevis (ad″). By reflecting the triceps, one sees (Figs. 84, 85) the ilio psoas (ip), and beneath the semimembranosus, the quadratus (qf), and capsularis femoris (og).

Description of the separate Muscles.

(A.) Muscles of the dorsal surface.

*109.* M. glutaeus (Fig. 80 gl).

*Dugès*, ex-ilio-trochantérien.--*Zenker*, glutaeus maior.

The tendinous origin of this muscle is found on the outer surface and upper border of the two hinder thirds of the iliac bone. Thence it runs outwards and backwards between the head of the m. vastus externus (ve) on the one side, and the ilio-psoas and rectus anticus (ra) on the other, to be inserted into a tubercle (trochanter) of the femur.

*110.* M. Pyriformis (Fig. 80 p).

*Cuvier*, pyramidal.--*Dugès*, coccy-fémoral, n. 136.

A narrow, slender muscle, arising from the apex of the coccyx; it passes obliquely outwards and backwards to the thigh, to be inserted deeply between the m. vastus externus and the biceps, into the inner surface of the femur, but towards the ventral surface.

M. triceps femoris s. extensor cruris communis (Fig. 80).

*Dugès*, pelvi-fémoro-rotulien, n. 145, 146, 147.

This is a large, strong muscle, having three heads of origin, and inserted by a tendon into the tibio fibula. The three heads are the caput longum or the rectus femoris anticus (r.a.), the caput externum or the vastus externus (v.e.), and the caput internum or the vastus internus (Fig. 82 vi); of these, the first is situated on the outer border of the thigh, the second on the dorsal surface, and the third on the ventral surface.

Muscles of left thigh of Rana esculenta. Dorsal view.

b M. biceps. ci M. coccygeo-iliacus. g M. gastrocnemius. gl M. glutaeus. p M. pyriformis. pe M. peroneus. r.a. M. rectus anterior. ri″ M. rectus internus minor. sm M. semimembranosus. t.a. M. tibialis anticus. tr. M. triceps fem. v.e. M. vastus externus. ]

*111.* [*a.*] M. rectus femoris anticus (Figs. 80, 82 ra).

This arises from the under (ventral) surface of the iliac bone about its middle and beneath the m. glutaeus. The muscular belly quickly passes into an aponeurosis, which covers the other two muscular masses and combines with their tendons.

*112.* [*b.*] M. vastus externus (Fig. 80 v.e.).

It arises from the upper and hinder extremity of the iliac bone (Fig. 42 il′) behind the glutaeus, which here sinks in between this muscle and the rectus anterior.

*113.* [*c.*] M. vastus internus (Figs. 81, 82 vi).

It arises from the whole of the under and outer surfaces of the hip-joint capsule, and from tendinous slips which pass from this capsule downwards on the under surface of the muscle, (from the pubis and the femur I have not seen any fibres of origin, as stated by others). Anteriorly the vastus may easily be separated into two heads. The two vasti unite and form one muscular belly, in the formation of which, as above stated, the rectus anticus takes no part. This united muscle passes into a tendon which, without the mediation of a patella, passes over the knee-joint to be inserted into the anterior extremity of the tibio fibula, and is prolonged into the fascia of the leg.

*114.* M. ilio-fibularis s. biceps (Fig. 80 b).

*Dugès*, ilio-péronien, n, 149.--*Zenker*, flexor externus tibiae, p. 42.

This is a long, somewhat narrow muscle, which lies to the inner side of, and partly covered by, the vastus externus, between which and the semimembranous it is placed. It arises by a tendon between the ilio-psoas and pyriformis from the ilium above the acetabulum and behind the origin of the vastus externus. From here it passes backwards, separated from the vastus externus by a strong ligam. intermusculare. On the inner side of this muscle, between it and the m. semimembranosus, run the vessels of the thigh and the N. ischiadicus. The muscle then divides into two portions, of which one is inserted high up on the inner and under surface of the femur. This is probably the muscle which Klein (l. c., p. 61) describes as the extensor brevis. The other long muscular belly passes into a thin tendon, opposite the hinder extremity of the thigh, it divides into two portions; the anterior is inserted into the dorsal surface of the hinder extremity of the femur, the other into the dorsal surface of the tibio-fibula. Between the two is stretched an arch with the concavity outwards. This insertion of the biceps is covered by the stronger tendon of origin of the m. gastrocnemius (compare Fig. 87).

*115.* M. semimembranosus (Figs. 80, 86 sm).

*Dugès*, sus-ischio-poplité, n. 148.--*Klein*, p. 60, extensor femoris sublimis.

This muscle lies on the dorsal surface of the thigh, to the inner side of the biceps and pyriformis: it is a broad muscle, which takes a tendinous origin from the hinder and upper angle of the symphysis ossis ilei, and is inserted by a flat tendon into the dorsal surface of the ligaments of the knee-joint, and through these into the tibio-fibula. The tendon is formed rather abruptly from the muscle, and is surrounded (Fig. 86) by the concave arch, which forms the tendon of origin of the gastrocnemius (q. v.). A little behind its middle (compare Fig. 81) the muscle is divided obliquely into an anterior and a posterior portion by an aponeurotic septum. As all the fibres are interrupted by this structure, the muscle may very easily be torn through.

(B.) Muscles on the ventral surface.

*116.* M. sartorius (Figs. 81, 82 s).

*Dugès*, sous-iléo-tibial, n. 150.--*Klein*, gracilis.

This long, flat muscle lies along the middle of the ventral surface of the thigh; it arises by a tendon from the anterior inferior angle formed by the symphysis of the innominate bones, and terminates in a tendon behind the knee-joint, forming a kind of pes anserinus in the fascia of the leg, similar to that of the semitendinosus.

*117.* M. rectus internus major (Ecker), (Figs. 81 r.i′, 82 ri′).

*Dugès*, post-ischio-tibial profond, n. 152.--*Klein*, semimembranosus.

This is a broad and flat muscle, thinned out at either extremity; it occupies the inner half of the ventral surface of the thigh, and is in relation with the adductor magnus externally and anteriorly, with the sartorius posteriorly, and the rectus minor muscle internally. The muscle arises by a tendon from the pubic symphysis; it covers in its course the semitendinosus, then passes into a strong tendon, which blends with the tendon of the rectus minor, to be inserted by a slip into a process of the tibio-fibula representing the tuberositas tibiae; first passing between the tendons of the sartorius and semimembranosus, which here form an aponeurotic arch; a second slip passes under the tendon of the m. semitendinosus to be inserted into the upper surface of the tibio-fibula, under it passes the N. tibialis. A third thread-like tendon passes to the m. semimembranosus. Somewhat behind its middle (Fig. 82) the muscle is traversed by an inscriptio tendinea, by which the whole of the fibres are interrupted.

Muscles of left thigh of Rana esculenta. Ventral surface.

ad′ M. adductor longus. ad″ M. adductor brevis. ad‴ M. adductor magnus. e.c. M. extensor cruris. f.t. M. flexor tarsi. g.c. M. gastrocnemius. r.i′ M. rectus internus major. r.i″ M. rectus internus minor. s M. sartorius. t.a. M. tibialis anticus. t.p. M. tibialis posticus. v.i. M. vastus internus. ]

*118.* M. rectus internus minor (Ecker), (Figs. 80, 81 r.i″).

*Dugès*, post-ischio-tibial superficiel, n. 151.--*Zenker*, flexor tibiae magnus.--*Klein*, ischio-tibialis.

Situated entirely on the inner surface of the thigh, this narrow muscle arises by a tendinous band which runs the whole length of the pubic symphysis, and is connected posteriorly with the sphincter ani, anteriorly with the rectus abdominis; posteriorly it passes into a thin tendon which is also connected with the muscle just described (117). In its course this muscle is attached to the skin by strands of vessels and connective tissue.

The vastus internus major and minor together undoubtedly correspond with rectus internus or gracilis of human anatomy. The rectus internus major is, however, regarded as corresponding with the adductor magnus by Dugès, and with the semimembranosus by Klein; by considering the position and attachments of these muscles one must arrive at a different conclusion.

MM. adductores femoris.

*119.* [*a*] M. adductor longus (Fig. 82 ad′).

*Dugès*, sous-ilio-fémoral, n. 141.

Without further dissection this muscle is only partially visible between the m. sartorius and vastus internus (Fig. 81 ad′). The muscle is flat and long, and arises by a tendon from the anterior inferior angle of the pubic symphysis (Fig. 42 s), partially covered by the origin of the sartorius. Thence the muscle passes between the vastus internus and the adductor magnus, and finally is inserted below the middle of the femur, together with the latter muscle.

Muscles of the left thigh of Rana esculenta. Ventral surface.

ad′ M. adductor longus. ad‴ M. adductor magnus. gl M. glutaeus. ip M. ilio-psoas. ra M. rectus fem. anticus. ri′ M rectus int. major. s M. sartorius. st M. semitendinosus. vi M. vastus internus. ]

*120.* [*b*] M. adductor magnus (Figs. 81, 82 ad‴).

*Dugès*, sous-ischio-pubi-fémoral (adductor 1 and 2), n. 142, 143.--*Klein*, adductor magnus and extensor femoris profundus.

This muscle is visible between the sartorius and rectus internus major in the anterior half of the thigh, posteriorly it is covered by these muscles. It arises by a tendon from (a) the pubic symphysis and ischii, and is in this position divided into two portions, between which passes the tendon of one head of the m. semitendinosus (Fig. 83 st″); (b) a second part arises from this same tendon (Fig. 83 st‴) and joins with the first part. Thus formed the muscle passes to be inserted into the distal half of the inner surface of the femur as far as the condyle. Near its hinder extremity, however, it passes on to the dorsal and outer surfaces, and thus forms a kind of muscular sheath surrounding the distal portion of the bone.

*121.* [*c*] M. adductor brevis (Figs. 81, 83 ad″),

and

*122.* [*d*] M. pectineus (Fig. 83 pe).

*Dugès*, sous-pubio-fémoral (analogue of the pectineus, possibly of the add. brevis also).

These two small muscles which lie under cover of the sartorius, adductor longus and magnus, appear externally as one muscle, but may easily be separated (Fig. 83). They arise close together from the pubic symphysis, and are inserted into the inner surface of the anterior half of the femur. They are not attached to the adductor magnus.

Deep muscles of left thigh of Rana esculenta.

ad′ M. adductor longus. ad″ M. adductor brevis. ad‴ M. adductor magnus. ip M. ilio-psoas. pe M. pectineus. ra M. rectus anticus, ri′ M. rectus internus major } ri″ M. rectus internus minor } cut through. s M. sartorius. st Belly of m. semitendinosus. st′ M. semitendinosus (cap. posticum). st″ M. semitendinosus (cap. anticum). st‴ Fibres passing into the adductor magnus. vi M. vastus internus. ]

*123.* M. semitendinosus (Fig. 83 st, st′, st″).

*Dugès*, bis-ischio-tibial, n. 153.--*Zenker*, biceps.

This is a long thin muscle, only visible after removal of the m. rectus internus, by which it is entirely covered. It arises by two long thin tendons, one (caput posticum, st′) from the pubic symphysis, the other (caput anticum, st″) from the hollow between the symphysis and the acetabulum. The latter passes through a slit in the adductor magnus, and so affords this muscle another point of origin; then backwards between the adductor magnus and the rectus internus major and under the lower third of the thigh, and unites with the posterior head of origin. The muscle so formed passes into a thin tendon, and, together with that of the sartorius, forms an aponeurotic arch, connected with the fascia of the leg, under which the tendons of the rectus internus major and minor pass.

(C.) Deep muscles of the thigh.

To these, in addition to the adductor brevis, pectineus, and the portion of the biceps already described, belong also the following:

Deep muscles of the left thigh of Rana esculenta. Dorsal view.

ad′ M. adductor brevis. ci M. coccygeo-iliacus. cx Coccyx. gl M. glutaeus. il Ileum. ip M. ilio-psoas. o.g. M. obturatorius. qf M. quadratus femoris. ]

Left half of pelvis of Rana esculenta. Thigh turned forwards under the abdomen.

gl M. glutaeus. og M. obturatorius. ]

*124.* M. ilio-psoas (Figs. 82, 83, 84 ip).

*Dugès*, intra-ilio-fémoral (*iliacus and psoas).--*Cuvier*, *Zenker*, *Klein*, iliacus internus.

The fibres of this muscle take a broad origin from the pelvic surface of the ilium, pass outwards over the lower margin of the bone and form a flat muscle with its apex pointed posteriorly. It crosses the hip-joint between the m. rectus and vastus internus, covering the hinder part of the m. glutaeus, and is inserted into the outer surface of the middle third of the femur.

*125.* M. quadratus femoris (Fig. 84 qf).

*Dugès*, post-ilio-fémoral (Homologue of the glutaeus maximus), n. 197.--*Zenker*, glutaeus minor, p. 42.

This muscle is of a somewhat elongated, triangular shape, and arises, under cover of the pyriformis, from the ilium behind the acetabulum; it passes backwards over the joint to be inserted into the inner and under surfaces of the femur, between the pyriformis and ilio-psoas; below, it is in direct relation with the adductor brevis.

*126.* M. obturatorius (Figs. 84, 85 og).

*Dugès*, ischio-pubi-fémoral, n. 139 (?).--*Zenker*, m. capsularis femoris.

This small muscle is deeply situated upon the hip-joint, and covered by all the other muscles that arise from the symphysis. Its origin from the innominate bone extends from the superior posterior angle of the symph. ossis ilii to about the middle of the pubic symphysis; the muscle fills the space between the crest of the symphysis and the acetabulum. The fibres converge to pass into a strong tendon, which is inserted into the posterior and anterior surfaces of the head of the femur. The muscle appears to represent collectively the small rotators of human anatomy, m. obturator externus and internus and the gemelli.

II. MUSCLES OF THE LEG.

General description.

On the outer surface (the anterior of man), covered by the fascia cruris, into which the tendon of the extensor communis cruris or triceps is prolonged, are found the following muscles: nearest to the bone, the m. extensor cruris brevis (ec); externally, the m. tibialis anticus (ta) and the m. peroneus (pe). On the inner surface (the hinder of man) lie the gastrocnemius (gc) and tibialis posticus (tp), and deeply the flexor tarsi sup. (ft).

*127.* M. gastrocnemius (Figs. 80, 81, 86).

*Dugès*, bi-fémoro-plantaire, n. 159.

This important muscle arises by two tendinous heads. The one (Fig. 86 g′) rather nearer the middle line of the popliteal space, is by far the stronger: it arises by a broad, tendinous expansion, which covers the knee-joint, and is attached to the femur and the tibio-fibula by anterior and posterior bands respectively; it ends internally in a concave aponeurotic arch: the second head is a thin, tendinous slip, arising from the common tendon of the triceps as this lies on the knee-joint. The muscle is thickest near its origin, and then gradually diminishes in size as it passes backwards; the superficial surface is convex, the deep surface is flat. By tracing the tendons of origin, they are seen soon to unite and form a common flat tendinous surface, broad in front, contracted behind; this aponeurosis lies in a plane running obliquely from the deep surface towards the superficial surface, without, however, reaching this. The muscular fibres arise from both surfaces of the aponeurosis, the fibres of the two sides diverging slightly as they pass backwards so as to be inclined at a small angle to each other. The fibres are inserted into a fibrous expansion (Ap) which lies on the superficial surface of the muscle; thin and slight in front, this aponeurosis rapidly thickens posteriorly until it passes into the tendo Achillis.

Muscles of the right leg and foot of Rana esculenta. Dorsal view.

a.h. M. abductor hallucis. a.l1 M. abductor longus digiti I. A.p. Aponeurosis plantaris. b M. biceps. e.t. M. extensor tarsi. F.l. M. flexor digitorum III, IV, V longus. F.l′. M. flexor digitorum I and II longus. g M. gastrocnemius, drawn towards the right. g′ Tendon of origin of gastrocnemius. l.c. Ligamentum calcanei. p M. plantaris. r.i. MM. internus maior and minor. s.m. M. semimembranosus. s.t. M. semitendinosus. t.A. Tendo Achillis. t.A′. Thickening of tendo Achillis. t.p. M. tibialis posticus. v.e. M. vastus externus. v.i. M. vastus internus. ]

*128.* M. tibialis posticus (Fig. 86 t.p.).

*Dugès*, cruro-astragalien, n. 160.

Covered by the gastrocnemius this muscle occupies the whole of the inner and upper surfaces of the tibio-fibula, from which it arises by numerous fibres. Opposite the hinder extremity of the bone the muscle becomes free and passes somewhat abruptly into a tendon, which courses behind and over the malleolus internus, on to the dorsum of the foot, and is here inserted into the anterior extremity of the astragalus. I cannot agree with Dugès that this muscle corresponds with the soleus (Ecker).

*129.* M. extensor cruris brevis (Fig. 87 ec).

*Dugès*, pré-fémoro-tibial, n. 154.

Covered by the strong fascia cruris, and lying between the m. tibialis anticus and the tibio-fibula, this muscle arises by a long tendon from the inner condyle of the femur; it passes backwards in the groove on the anterior extremity of the tibio-fibula, covered by the tendon of the triceps femoris, and is then inserted by muscular fibres into the outer surface of the tibio-fibula almost as far as the posterior third of the bone. (Dugès regards this muscle as the upper, i. e. anterior, portion of the tibialis anticus.)

*130.* M. tibialis anticus (Figs. 80, 81, 87 ta).

*Dugès*, pré-fémoro-astragalien and pré-fémoro-calcanien, n. 156 and 157; the former he regards as one part of the tib. anticus, the latter as the peroneus longus I.--*Zenker*, tib. ant. biceps.

The tendon of origin of this muscle is attached to the femur near the tendon of the m. extensor cruris brevis, and to the joint-ligaments. The muscle is placed under the fascia cruris, its long tendon of origin passing beneath the tendon of the triceps in a special sheath through the joint; the tendon then gains a muscular belly which bifurcates at about the middle of the leg, forming two muscular masses, coursing along the outer and the inner side of the leg respectively. The latter is inserted into the dorsal surface of the astragalus by a tendon, and the former into the dorsal surface of the calcaneus in a similar manner. The muscle extends the foot and flexes the tarsus; the latter movement is very distinct on account of the insertion of the muscle being so near the hypomochlion.

*131.* M. flexor tarsi anterior (Ecker), (Fig. 87 Ft).

*Dugès*, ex-tibio-astragalien, n. 155.--*Zenker*, tibialis anticus simplex.

This muscle arises where the insertion of the extensor cruris brevis ceases, from the middle of the under surface of the tibio-fibula, and passes backwards between the two tendons of the m. tibialis anticus along the outer side of this muscle, to be inserted by a tendon into the inner side of the anterior articular extremity of the astragalus and the fascia dorsalis pedis.

Muscles of leg and foot of Rana esculenta, seen from below.

a.b.5 M. abductor dig. V longus. ec M. extensor cruris brevis. e.d.1 M. extensor digit I longus. e.d.4 M. extensor digit IV longus. e.d.5 M. extensor digit V longus. Ft M. flexor tarsi anterior. Ft′ M. flexor tarsi posterior. g M. gastrocnemius. p M. peroneus. ta M. tibialis anticus. tF M. triceps femoris. ]

*132.* M. peroneus (Figs. 80 pe, 87 p).

*Dugès*, génio-péronéo-calcanien, n. 158.

This is a strong muscle which is attached by a long tendon of origin to the hinder extremity of the femur and the ligaments of the knee-joint. The tendon runs in a sheath through the joint and posteriorly becomes muscular; the muscle passes downwards on the outer side of the tibio-fibula to be inserted into the malleolus externus of this bone and into the anterior extremity of the calcaneus. It has an action similar to that of the m. tibialis anticus.

III. MUSCLES OF THE FOOT.

A. MUSCLES ON THE PLANTAR SURFACE.

*133.* Aponeurosis plantaris (Fig. 88 A.p.).

As already mentioned, the tendon of the m. gastrocnemius is, at the heel, continued into a strong aponeurosis, and possesses at this place a thickening. The aponeurosis is of triangular form, the base directed towards the toes and attached to these. The lateral borders of this triangle are continued into weaker fasciae, which are attached to the two long tarsal bones. The inner border in particular gives a strong bundle of fibres to the astragalus, and is thus connected with the fascia of the dorsum of the foot; externally this aponeurosis is attached to a cartilage (Dugès, os sesamoïde, l. c., n. 66), situated on the plantar surface of the joint between the calcaneus and the os metatarsi IV.

*134.* Ligamentum calcanei (Ecker), (Figs. 88, 89 l.c.).

If the tendo Achillis be divided and the aponeurosis plantaris reflected towards the toes, there is seen, arising from the posterior head of the tibio-fibula, in its whole breadth, a ligament (between the tib. posticus and peroneus). This ligament forms a firm surface on which the thickened portion of the tendo Achillis may move, and which evidently represents the tuberosity of the heel bone. I have therefore named the entire structure the ligamentum calcanei.

Muscles of the right leg and foot of Rana esculenta. Dorsal view.

a.h. M. abductor hallucis. a.lI M. abductor longus digiti I. A.p. Aponeurosis plantaris. b M. biceps. e.t. M. extensor tarsi. F.l. M. flexor digitorum III, IV, V longus. F.l.′ M. flexor digitorum I and II longus. g M. gastrocnemius, drawn towards the right. g′ Tendon of origin of gastrocnemius. l.c. Ligamentum calcanei. p M. plantaris. r.i. MM. internus maior and minor. s.m. M. semimembranosus. s.t. M. semitendinosus. t.A. Tendo Achillis. t.A′. Thickening of tendo Achillis. t.p. M. tibialis posticus. v.e. M. vastus externus. v.i. M. vastus internus. ]

Several muscles arise from this ligament, viz.:--

*135.* M. extensor tarsi (Klein), (Figs. 88, 89 e.t.).

*Dugès*, tibio-sous-astragalien (regarded by him as the homologue of the tibialis posticus).

Covered by the two succeeding muscles, this muscle arises from the ligamentum calcanei, runs backwards, and is inserted into the whole length of the plantar surface of the astragalus. It extends the foot.

*136.* M. plantaris (Figs. 88, 89 p).

This takes its origin from the ligamentum calcanei to the inner side and below the last muscle. It passes backwards and is inserted into the dorsal surface of the aponeurosis plantaris.

Muscles of the plantar surface of foot of Rana esculenta, twice natural size.

A.p. Aponeurosis plantaris, divided. ab.5. M. abductor dig. V. ad.5. M. adductor dig. V. ad.l.1. M. adductor longus dig. I. e.t. M. extensor tarsi. F.5. M. flexor brevis dig. V. F.l. M. flexor digitorum III, IV, V longus. F.l′. M. flexor digitorum I, II longus. l.1.} l.2.} l3 } l3′ } Musculi lumbricales. l4′ } 14″ } l.5.} l.c. Ligamentum calcanei. p M. plantaris. t.A. Tendo Achillis. t.A′. Thickening in tendo Achillis. t.p. M. transversus plantae posterior. t.p.′ M. transversus plantae anterior. ]

*137.* M. flexor digitorum III, IV, V longus (Ecker), (Figs. 88, 89 F.l.).

*Dugès*, péronéo-sous-phalangettien (flexor dig. longus).

This muscle also arises from the ligamentum calcanei to the outer side of the m. plantaris. It runs backwards over the aponeurosis plantaris, and at the free margin of this passes somewhat suddenly into a strong tendon, which traverses an aponeurotic canal, formed by fibres of the aponeurosis passing above and below the tendon, from the cartilaginous enlargement in the tendon to the median border of the aponeurosis. The tendon forms three slips for the fifth, fourth, and third toes: these are slightly attached to the aponeurosis, but reach beyond its free border to be inserted into the terminal phalanges of the toes mentioned, and are held down by fibrous bands. (The small m. lumbricales arising from these tendons are described below.)

*138.* M. flexor digitorum I, II longus (Ecker), (Figs. 88, 89 F.l′.).

The tendons, by means of which the terminal phalanges of the first and second toes are flexed, arise directly from the posterior border of the aponeurosis.

*139, 140.* MM. transversi plantae (Ecker), (Fig. 89 t.p., t.p′.).

The movements of the aponeurosis and through it the movements of the tendons attached to it are influenced not only by the m. gastrocnemius and plantaris, but also by two other muscles, which together have been described as the flexor dig. longus internus (Klein), or as the tarso-sous-phalangettien (Dugès, 221).

*a.* M. transversus plantae posterior (t.p.).

This takes its origin from the plantar cartilage, widens as it courses backwards and inwards to be inserted into the dorsal surface of the aponeurosis plantaris; from this the tendons for the first and second toes (flexor dig. longus I and II) arise, thus there is no direct connection between the muscular fibres of the two muscles.

*b.* M. transversus plantae anterior (t.p′.).

This muscle is covered by the last; broader anteriorly, it arises from the calcaneum, and is inserted to the inner side of the last muscle into the dorsal surface of the aponeurosis. This muscle, like that just described, is not continued directly into the tendon of the flexor of the toes, they cannot therefore be regarded as flexors of the toes.

*141* to *149*. Musculi lumbricales (Fig. 89 l.1–5).

(A.) From the posterior border of the aponeurosis plantaris arise:--

(1) M. lumbricalis digiti I (l.1).

*Dugès*, tendini-sous-phalangien de pouce, n. 185.

This is inserted into the anterior extremity of the proximal phalanx.

(*2*) M. lumbricalis digiti II (l.2).

*Dugès*, tendini-sous-phal. du I doigt, n. 186 (and 187), double according to Dugès.

Similarly inserted.

(*3* and *4*) MM. lumbricales digiti III (l.3).

*Dugès*, tendini-sous-phal. du III doigt, n. 188, single according to Dugès.

One of these (l3) is inserted into the anterior extremity of the basal phalanx, the other (l3′) into a corresponding position on the middle phalanx.

(*5*) M. lumbricalis digiti IV.

*Dugès*, tendini-sous-phal. du IV doigt.

Inserted into the anterior extremity of the basal phalanx.

(B.) Arising from the tendons of the flexor longus III, IV, V:

(*6* and *7*) MM. lumbricales digiti IV (l.4′. and l.4″.).

*Dugès*, tendini-sous-phalanginien du IV doigt, n. 201, 202.

The first (l.4′) is inserted into the posterior end of the basal phalanx, the second (l.4″) in a similar position into the second phalanx.

(*8*) M. lumbricalis digiti V (l.5.).

*Dugès*, tendini-sous-phalangien du V doigt, n. 203.

This arises from the tendon for the fifth toe, runs backwards as a thin tendon alongside that of the flexor, and is inserted into the middle phalanx.

Special Muscles of the Separate Toes.

(I.) Muscles of the rudimentary great toe.

*150.* M. abductor hallucis (Figs. 88 a.h., 90).

*Dugès*, tibio-sous-tarsien, n. 163.

This muscle arises from the inner border of the aponeurosis plantaris, at the spot where the m. plantaris is inserted, it may therefore almost be regarded as a continuation of this muscle; it is inserted into the anterior border of the rudimentary toe.

(II.) Muscles of the great and first toes.

*151.* M. adductor longus digiti I (Figs. 89, 90 ad.l1).

*Dugès*, calcanéo-scaphoidien, n. 164.

This powerful muscle arises from the plantar surface of the calcaneum and astragalus; its fibres converge towards a tendon lying in its middle, which becomes free towards its posterior end; the tendon passing inwards under the ligamentum tarsi transversum through a groove on the hinder extremity of the astragalus in an arched direction, to be inserted into the os naviculare, which bears the rudimentary great toe and the os metatarsi I.

(III.) Muscles of the first toe.

*152.* M. abductor longus digiti I (Figs. 88 al.1, 90 a.b.1).

It takes its origin from the inner border of the aponeurosis plantaris, and lies on the plantar surface of the abductor hallucis. Its tendon runs in the hollow which the great toe forms, and is inserted into the inner side of the os metatarsi I.

*153.* M. flexor brevis digiti I (Fig. 90 F.b.1).

A small, thin muscle, which arises from the anterior extremity of the os metatarsi II, and is inserted into the basal phalanx of the first toe. In this small muscle, and also in the m. lumbrical. dig. V (Fig. 89 l.5.), the nerve distribution may be very well seen.

*154.* M. opponens dig. I (Fig. 90 op).

*Dugès*, sous-metatarso-phalangien du pouce, n. 192.

This is situated to the inner side of the preceding muscle, arises from the os metatarsi II somewhat narrow, widens in a fan-like manner towards the os metatarsi I, into the anterior half of which it is inserted.

(IV.) Muscles of the second toe.

*155.* M. flexor metatarsi dig. II (Fig. 90 F.m.2).

*Dugès*, sous-tarso-metatarsien du II doigt.--*Klein*, extensor metatarsi.

By a narrow origin from the hinder end of the calcaneum, posteriorly this muscle becomes broader and is inserted, somewhat thinned out, into the plantar surface of the second os metatarsi.

*156.* M. flexor dig. II proprius (Fig. 90 F.p.2).

*Dugès*, sous-metatarso-phalangien, n. 194.

It arises from the plantar surface of the os metatarsi II, and is inserted by a thin tendon into the plantar surface of the first phalanx.

Dugès describes this and the analogous muscles of the third, fourth, and fifth toes (F.p.3, 4, 5) as the interossei plantares, a nomenclature which, to me, does not appear correct, as these muscles lie entirely on the plantar surface, and do not adduct or abduct the toes, but flex them.

(V.) Muscles of the third toe.

*157.* M. flex. metatarsi dig. III (Ecker), (Fig. 90 F.m.3).

*Dugès*, sous-calcaneo-métatarsien du III doigt, n. 174.-- *Klein*, extensor metatarsi.

Like the corresponding muscle of the second toe (n. 155), this arises by a small tendon from the hinder extremity of the calcaneum, runs backwards and is inserted into the plantar surface of the os metatarsi III. The greatest portion of the muscle lies beneath the m. transversus metatarsi (tm), the most anterior portion, however, lies above this. Dugès has described this latter portion as a special muscle (n. 176, metatarso-métatarsien du III), the same description holds good for the second toe (n. 177, Dugès).

*158.* M. flexor dig. III proprius (Ecker), (Fig. 91 Fp3).

*Dugès*, sous-métatarso-phalangien du III doigt, n. 195.

Like the corresponding muscle of the second toe, this arises from the plantar surface of the os metatarsi III, and is inserted by a thin tendon into the plantar surface of the anterior extremity of the first phalanx.

Muscles of plantar surface of foot of Rana esculenta.

a.b.1 M. abductor longus digiti I. ab5 M. abductor digiti V. ad.l.1 M. adductor longus digiti I. a.h. M. abductor hallucis. F.b.1 M. flexor brevis digiti I. F.m.2, 3, 4 M. flexores metatarsi II, III, IV. F.p.2, 3, 4, 5 MM. flexor. proprii digit. 2, 3, 4, 5. F.ph.3, 4, 4′, 5 MM. flexor. phalang. digit. 3, 4, 5. op M. opponens digiti I. t.m′ } t.m″ } MM. transversi metatarsi 1, 2, 3. t.m‴ } ]

*159.* M. flexor phalangum proprius digiti III (Ecker), (Fig. 91 F.ph.3).

*Dugès*, phalango-phalangien, n. 204.

This arises by tendon from the plantar surface of the basal phalanx, and is inserted into the anterior extremity of the terminal phalanx.

(VI.) Muscles of the fourth toe.

*160.* M. flexor metatarsi dig. IV (Fig. 91 F.m.4).

*Dugès*, métatarso-métatarsien, n. 175.

Similarly to the corresponding muscle of the third toe, this one arises from the hinder extremity of the calcaneum, and is inserted into the anterior portion of the plantar surface of the os metatarsi IV, but not into the greater portion of this surface, as in the second and third os metatarsi.

*161.* M. flexor dig. IV proprius (Fig. 91 Fp4).

*Dugès*, sous-métatarso-phalangien du IV doigt (interosseus plantaris), n. 196.

The origin and insertion are similar to those of the muscles of the second and third toes.

Muscles of plantar surface of foot of Rana esculenta.

a.b.1 M. abductor longus digiti I. ab5 M. abductor digiti V. ad.l.1 M. adductor longus digiti I. a.h. M. abductor hallucis. F.b.1 M. flexor brevis digiti I. F.m.2, 3, 4 M. flexores metatarsi II, III, IV. F.p.2, 3, 4, 5 MM. flexor. proprii digit. 2, 3, 4, 5. F.ph.3, 4, 4′, 5 MM. flexor. phalang. digit. 3, 4, 5. op M. opponens digiti I. t.m′ } t.m″ } MM. transversi metatarsi 1, 2, 3. t.m‴ } ]

*162.* M. flexor brevis dig. IV.

A small muscle, which arises with the m. flexor brevis of the fifth toe, from enlargement of aponeurosis plantaris, and is inserted into the basal phalanx of the fourth toe.

*163.* M. flexor phalangum proprius dig. IV anterior (Fig. 91 F.ph.4).

*Dugès*, phalango-phalanginien, n. 205.

It resembles the corresponding muscle of the third toe.

*164.* M. flexor phalangum proprius posterior (Fig. 91 F.ph.4′).

*Dugès*, phalangino-phalangettien, n. 209.

This extends from the plantar surface of the second phalanx to the anterior extremity of the third.

(VII.) Muscles of the small toe.

*165.* M. abductor dig. V (Fig. 91 a.b.5).

*Dugès*, calcanéo-ex-métatarsien du digitule, n. 169.

This muscle arises from the hinder extremity of the calcaneum, and is inserted into the outer surface of the fifth metatarsal.

*166.* M. adductor dig. V (Fig. 89 a.d.5).

*Dugès*, sous-tarso-in-phalangien, n. 191.

This arises from the cartilage of the plantar aponeurosis, and is inserted into the hinder end of the fifth metatarsal.

*167.* M. flexor brevis dig. V (Fig. 89 F.5).

*Dugès*, sous-tarso-ex-phalangien, n. 190.

Arising from the same place as the preceding, it extends to the basal phalanx.

*168.* M. flexor dig. V. proprius (Fig. 91 F.p.5).

(Analogues of Muscles, n. 156, 158, 161; see note at n. 156).--*Dugès*, sous-métatarso-phalangien, n. 197 (*inteross. plant.).

This muscle arises from the plantar and inner surfaces of the fifth metatarsal, and is inserted into the basal phalanx.

*169.* M. flexor phalangum proprius (Fig. 91 F.ph.5).

*Dugès*, phalango-phalanginien, n. 206.

Its origin and insertion are as in the corresponding muscles of the second, third, and fourth toes, n. 159, 163, 164, 169.

*170* to *172*. MM. interossei (Fig. 91 t.m.).

*Dugès*, 1, 2, and 3, intermétatarsien, n. 170, 171, 172.

These are three muscles with their fibres arranged transversely, which occupy the anterior portion of the spaces between the metatarsals, and approximate these. The first arises (tm′) from the edge of the plantar surface of the first metatarsal, and is inserted into the corresponding part of the second: the second (tm″) passes from this point to the third, and the third (tm‴) to the fifth.

B. MUSCLES OF THE DORSAL SURFACE.

*173.* M. flexor tarsi posterior (Ecker), (Fig. 92 F.t.).

*Dugès*, péronéo-sus-astragal, n. 161.

This is a strong muscle, which has a narrow origin from the outer side of the tibio-fibula, directly over the distal extremity, and is inserted into the dorsal surface of the astragalus from the middle to the distal extremity.

Muscles of the first toe.

*174.* M. extensor longus dig. I (Fig. 92 e.l.1).

*Dugès*, calcanéo-sus-métatarsien du pouce, n. 166.

This lies to the outer side of and near the foregoing muscle; it arises by a long, strong head from the middle of the calcaneum, runs obliquely backwards and inwards to unite with a small head which arises from the common epiphysis of the astragalus and calcaneum, in common with the m. extensor dig. II. The muscle so formed passes into a flat tendon to be inserted into the basal phalanx of the first toe.

*175.* M. extensor brevis dig. I (Fig. 92 e.b.1).

A small, short muscle which arises from the os naviculare and is inserted into the dorsal surface of the first metatarsal.

*176.* M. abductor brevis dig. I (Fig. 92 a.b.1).

*Dugès*, ex-tarso-métatarsien du pouce, n. 168.

This small muscle is situated near the preceding; it arises from the first bone of the supplemental toe, and is inserted into the inner side of the first metatarsal.

Muscles of the second toe.

*177.* M. extensor dig. II longus (Fig. 92 e.l.2).

*Dugès*, calcanéo-sus-phalangien du II doigt, n. 182.

This arises from the calcaneum, in common with the m. extensor longus of the third toe, and is inserted into the basal phalanx of the second toe by a tendon.

*178.* M. extensor dig. II brevis (Fig. 92 e.b.2).

*Dugès*, astragalo-sus-phalangien du II, n. 183.

This is partly covered by the preceding muscle: it arises from the astragalus, and unites with the tendon of the preceding muscle.

Muscles of the third toe.

*179.* M. extensor dig. III longus (Fig. 92 e.l.3).

*Dugès*, sus-astragalo-phalangien du médius, n. 199.

This arises with the extensor longus of the second toe from the calcaneum: its tendon unites with that of the following muscle.

*180.* M. extensor dig. III brevis (Fig. 92 e.b.3).

*Dugès*, astragalo-sus-phalangien du médius, n. 181.

This muscle arises from the astragalus, and is inserted with the tendon of the preceding muscle into the dorsal surface of the basal phalanx.

Dorsal view of muscles of foot of Rana esculenta.

a.b.1 M. abductor brevis dig. I. e.b.1 M. extensor brevis dig. I. e.b.2 M. extensor brevis dig. II. e.b.3 M. extensor brevis dig. III. e.b.4 M. extensor brevis 1 dig. IV. e.b.4′ M. extensor brevis 2 dig. IV. e.b.5 M. extensor brevis dig. V. e.l.1 M. extensor longus dig. I. e.l.2 M. extensor longus dig. II. e.l.3 M. extensor longus dig. III. e.l.4 M. extensor longus dig. IV. e.l.5 M. extensor longus dig. V. F.t M. flexor tarsi posterior. i.2 to i.10 MM. interossei. ]

Muscles of the fourth toe.

*181.* M. extensor longus dig. IV (Fig. 93 e.l.4).

*Dugès*, péroneo-sus-phalangien du IV, n. 178.

A narrow muscle arising in common with the flexor tarsi inf., but external to it. It is inserted into the tendinous expansion on the dorsum of the toe.

*182.* MM. extensores dig. IV breves (Fig. 93 e.b.4 and e.b.4′).

*Dugès*, calcanéo-sus-phalangien and sus-calcanéo-phalanginien, n. 179 and 198.

These two small muscles arise from the calcaneum: one is inserted into the basal phalanx, the other, by means of a long thin tendon, passes along with the tendon of the corresponding m. interosseus to the second phalanx, to which it is attached.

Muscles of the fifth toe.

*183.* M. extensor dig. V longus (Fig. 93 e.l.5).

*Dugès*, calcanéo-sus-métatarsien, n. 165.

A strong muscle which covers almost the whole length of the calcaneum; it arises from the anterior extremity of this bone, runs backwards to the outer side of the dorsum of the foot, and is attached to the outer surface of the fifth metatarsal.

*184.* M. extensor dig. V brevis (Fig. 93 e.b.5).

*Dugès*, calcanéo-sus-phalangien du V, n. 180.

This is a long thin muscle, which, together with the muscle last described, arises from the calcaneum and is inserted into the basal phalanx of the fifth toe.

*185.* M. abductor dig. V brevis (Fig. 93 i.10).

This, the last m. interosseus, arises from the outer side of the fifth metatarsal, and is inserted into the hinder extremity of the second phalanx of the same toe.

*186* to *195*. MM. interossei dorsales (Fig. 93 i.1 to i.10).

First toe.

(1) The analogue of the first m. interosseus is the m. abductor brevis dig. I (a.b.1).

(2) The second m. interosseus (i.2) arises from the outer side of the first metatarsal, and is inserted into the outer surface of the second phalanx of the same toe, dorsally to the m. opponens and flexor brevis dig. I.

Second toe.

(3) The third m. interosseus (i.3) takes origin from the anterior part of the outer surface of the first metatarsal by a thin tendon; it is inserted into the inner surface of the second phalanx by a similar tendon.

(4) The fourth m. interosseus (i.4) arises from the outer side of the second metatarsal, and is inserted into the outer surface of the second phalanx.

Third toe.

(5) The fifth m. interosseus arises from the outer surface of the second metatarsal, and is inserted by a thin tendon into the inner surface of the second phalanx of the same toe.

(6) The sixth arises from the outer surface of the third metatarsal, and is inserted laterally by a thin tendon into the hinder extremity of the second phalanx of the same toe.

Dorsal view of muscles of foot of Rana esculenta.

a.b.1 M. abductor brevis dig. I. e.b.1 M. extensor brevis dig. I. e.b.2 M. extensor brevis dig. II. e.b.3 M. extensor brevis dig. III. e.b.4 M. extensor brevis 1 dig. IV. e.b.4′ M. extensor brevis 2 dig. IV. e.b.5 M. extensor brevis dig. V. e.l.1 M. extensor longus dig. I. e.l.2 M. extensor longus dig. II. e.l.3 M. extensor longus dig. III. e.l.4 M. extensor longus dig. IV. e.l.5 M. extensor longus dig. V. F.t M. flexor tarsi posterior. i.2 to i.10 MM. interossei. ]

Fourth toe.

(7) The seventh m. interosseus (i.7) arises by a thin tendon from the hinder extremity of the astragalus, and by fleshy fibres from the hinder extremity of the fourth metatarsal; it is inserted by a thin tendon into the inner surface of the second phalanx of the same toe.

Dorsal view of muscles of foot of Rana esculenta.

a.b.1 M. abductor brevis dig. I. e.b.1 M. extensor brevis dig. I. e.b.2 M. extensor brevis dig. II. e.b.3 M. extensor brevis dig. III. e.b.4 M. extensor brevis 1 dig. IV. e.b.4′ M. extensor brevis 2 dig. IV. e.b.5 M. extensor brevis dig. V. e.l.1 M. extensor longus dig. I. e.l.2 M. extensor longus dig. II. e.l.3 M. extensor longus dig. III. e.l.4 M. extensor longus dig. IV. e.l.5 M. extensor longus dig. V. F.t M. flexor tarsi posterior. i.2 to i.10 MM. interossei. ]

(8) The eighth m. interosseus (i.8) takes its origin from the outer surface of the fourth metatarsal and from the inner surface of the fifth: it is inserted into the hinder extremity of the second phalanx.

Fifth toe.

(9) The ninth m. interosseus (i.9) arises from the inner surface of the fifth metatarsal, and is inserted into the hinder extremity of the second phalanx.

(10) The tenth m. interosseus has already been described as the abductor digiti V brevis (Fig. 94 i.10).

If we take the fourth toe as the axis of movement, the first, third, fifth, seventh, eighth, and tenth mm. interossei will abduct from an imaginary line which runs through this toe. The second, fourth, sixth, and ninth will adduct towards this line. If we compare them with those of man (in whose case the second toe affords the central line), those of the first group must be regarded as mm. interossei dorsales, of the latter as plantares. Dugès holds all these interossei (with the exception of the first, abductor brevis dig. I) to be mm. interossei dorsales (métatarso-sus-phalangettiens, n. 210, 211, 212, 214, 215, 216, 218, 219). Those which I have described as flexores proprii digitorum, he regards as interossei volares.

V. MUSCLES OF THE SKIN.

*196.* M. cutaneus pectoris (Fig. 95 cp).

*Dugès*, abdomino-guttural, n. 53.--*Klein*, abdomino-cutaneus.--*Zenker*, subcutaneus pectoris.

This is an elongated quadrangular muscle, attached by its hinder margin to the side of the xiphisternum, and to the superficial surface of the aponeurosis of the m. obliquus externus. The fibres course forwards and slightly outwards to be inserted, at a very acute angle, into the skin: lying between the two muscles and attached to them on either side is a thin fascia, which, together with the muscles and the septum thoracicum, assists in closing a triangular space between these structures and the deeper muscles.

The thinness and transparency of this muscle render it especially suitable for the investigation of nerve-terminations.

Pectoral region of Rana esculenta.

cp M. cutaneus pectoris. p″ Port. abdominalis of the m. pectoralis. ]

*197.* M. cutaneus dorsi (Fig. 96 cd).

*Dugès*, pubio-dorso-cutané, n. 56.--*Zenker*, cutaneus iliacus.

This muscle has a narrow origin in the space between the muscles of the belly and of the thigh, and is here inserted into the fasciae, which are attached to the pubic symphysis; it passes inwards and upwards to the outer side of the anterior insertion of the m. rectus femoris anticus, then widens and is inserted by diverging fibres into the inner surface of the skin of the hinder portion of the back.

*198.* M. coccygeo-cutaneus.

*Dugès*, coccy-dorso-cutanés, n. 57.

The muscular fibres which Dugès has described under this name, lie covered by the m. pyriformis, behind the m. coccygeo-iliacus, etc., and above the muscles of the rectum. They arise from the hinder extremity of the urostyle: they appear to be connected with the rectal muscles, and pass outwards to be attached to the skin.

Among the cutaneous muscles may perhaps be included the m. submaxillaris (p. 62).

The fibrils passing from the flexor tendons to the warty bodies on the plantar surface of the toes are described with the skin (p. 373).

Hind portion of back and thigh of Rana esculenta.

cd M. cutaneus dorsi. cx. Coccyx. gl. M. glutaeus. H Skin reflected to left side. oc M. obliquus externus. rf M. rectus femoris anterior. sm M. semimembranosus. v.e M. vastus externus. ]