Part 110

FIG. 229.—MUSCLES OF HEAD OF DOG

a, Scutularis; b, c, anterior auricular muscles; d, helicis; e, antitragicus; f, f, zygomaticus, out of which a portion is cut; g, slip of panniculus; h, parotido-auricularis; i, masseter; k, malaris; l, levator nasolabialis; m, levator labii superioris proprius; n, dilatator naris lateralis; o, p, buccinator (buccalis, molaris); q, retractor anguli oris; r, digastricus; s, mylo-hyoideus; 1, base of concha; 2, parotid gland; 2′, parotid duct; 3, submaxillary gland; 4, submaxillary lymph glands; 5, buccal glands; 6, zygomatic arch; 7, maxilla; 8, dorsum nasi; 9, parotid lymph gland. (Ellenberger-Baum, Anat. d. Hundes.) ]

The =depressor labii inferioris= is absent, unless we recognize as such a thin stratum arising on the body of the mandible and spreading out in the orbicularis.

There are no special =nasal muscles=, the homologue of the lateral dilator ending almost entirely in the upper lip.

The =buccinator= is wide and very thin, and the two planes of fibers cross each other.

The =palpebral muscles= present no very noteworthy special characters.

MUSCLES OF MASTICATION

The =masseter= is large. It arises from the zygomatic arch, and extends beyond the branch of the jaw below and behind. Three strata may be recognized in its structure.

The =temporalis= is very large and strong, and contains much tendinous tissue. It arises from the temporal fossa and the orbital ligament.

The =digastricus= is usually not digastric, but is a strong, round, fleshy muscle, which arises on the paramastoid or styloid process and is inserted into the border and inner surface of the ramus at the level of the last molar teeth.

The stylo-mandibularis is absent.

HYOID MUSCLES

The =mylo-hyoideus= is well developed.

The =stylo-hyoideus= is very slender, and is inserted into the body of the hyoid bone: it is not perforated by the digastricus.

FIG. 230.—SUPERFICIAL MUSCLES OF DOG, AFTER REMOVAL OF PANNICULUS CARNOSUS.

1, Levator nasolabialis; 2, levator labii superioris proprius; 3, dilatator naris lateralis; 4, 4′, buccinator; 5, retractor anguli oris s. risorius; 6, zygomaticus; 7, malaris; 8, masseter; 9, digastricus; 10, scutularis; 11, other auricular muscles; 12, parotido-auricularis; 13, mylo-hyoideus; 14, sterno-hyoideus; 15, sterno-thyroideus; 16, splenius; 17, lumbo-dorsal fascia; 18, rectus abdominis; 19, obliquus abdominis externus; 19′, aponeurosis of preceding; 20, intercostal muscle; 21, sacro-coccygeus accessorius; 22, sacro-coccygeus superior; 23, sacro-coccygeus inferior; 24, great trochanter; 25, jugular vein; a, b, c, brachiocephalicus; d, clavicle; e, f, trapezius; g, serratus cervicis; h, omo-transversarius; i, latissimus dorsi; k, posterior deep pectoral; l, supraspinatus; m, m′, deltoid; n, infraspinatus; o, triceps, long head; o′, triceps, external head; p, brachialis; q, extensor carpi radialis; r, gluteus medius; s, gluteus superficialis; t, t′, tensor fascia latæ; u, sartorius; v, biceps femoris; v′, fascia lata; w, semitendinosus; x, semimembranosus; y, sartorius; z, gracilis; 26, pronator teres; 27, flexor carpi radialis; 28, flexor carpi ulnaris; 29, tibialis anterior; 30, popliteus; 31, 31′, deep digital flexor; 32, superficial digital flexor; 33, gastrocnemius; 34, spine of scapula; α, parotid gland, with α′, its duct; β, submaxillary gland; δ, submaxillary lymph glands; η, parotid lymph gland; ζ, inferior buccal glands. (After Ellenberger, in Leisering’s Atlas.) ]

The hyoideus transversus and =omo-hyoideus= are absent.

The =sterno-thyro-hyoideus= is large and arises chiefly on the first costal cartilage.

MUSCLES OF THE THORACIC LIMB

The =trapezius= is thin, and is not clearly divided into cervical and thoracic portions. Its line of origin extends from about the middle of the neck to the ninth or tenth thoracic spine, the right and left muscles meeting on a median fibrous raphé.

The =omo-transversarius= arises by a tendon on the lower part of the spine of the scapula (often partially blended with the trapezius), and is inserted into the wing of the atlas.

The =rhomboideus= consists of three parts. The =dorsal portion= (Rhomboideus thoracalis) is small; it arises from the fourth to the sixth or seventh thoracic spine, and is inserted into the inner surface (chiefly) of the dorsal angle of the scapula. The =cervical portion= (Rhomboideus cervicalis) arises from the ligamentum nuchæ as far forward as the second or third cervical vertebra, and is inserted into the inner surface of the cervical angle of the scapula. The =cephalic portion= (Rhomboideus capitis) is a continuation of the preceding which is inserted into the occipital crest.

FIG. 231.—VENTRAL MUSCLES OF HEAD, NECK, AND THORAX OF DOG.

a, Mylo-hyoideus; b, digastricus; c, sterno-hyoideus; c′, sterno-thyroideus; d, sterno-cephalicus; e, brachiocephalicus; f, subscapularis; g, superficial pectoral; h, deep pectoral; i, rectus abdominis; k, obliquus abdominis externus; l, long head of triceps; m, internal head of triceps; n, biceps brachii; o, brachialis; 1, 1′, 1″, submaxillary lymph glands; 2, thyroid gland; 3, external jugular vein. (Ellenberger-Baum, Anat. d. Hundes.) ]

The =latissimus dorsi= is extensive, and has a fleshy attachment to the last two ribs. Its lower edge blends near the shoulder with the panniculus.

The =mastoido-humeralis= contains in front of the shoulder a fibrous mass in which the clavicle is embedded. Anterior to this it separates into two diverging portions. The =dorsal portion= (M. cleido-cervicalis) is attached to the median raphé of the neck and to the occipital bone. The =ventral portion= (M. cleido-mastoideus) is attached to the mastoid process. The common mass posterior to the clavicle and the fibrous intersection, which is attached to the humerus, is homologous with the clavicular portion of the deltoid of man.

The =superficial pectoral= muscle is small. It arises on the sternum from the first to the third costal cartilage, and is inserted into the anterior surface of the humerus. A superficial slip detached from it is inserted into the fascia of the forearm. The =deep pectoral= has no prescapular portion. It arises on the sternum and costal cartilages from the second costal to the xiphoid cartilage. It is inserted chiefly into the internal tuberosity of the humerus, but also by small slips into the external tuberosity and the fascia of the arm.

The =serratus magnus= shows no clear division into cervical and thoracic portions. It arises from the last five cervical vertebræ and the first seven or eight ribs, and is inserted into the upper part of the costal surface of the scapula.