Part 51

Action.—Pulls the eyeball outward.

=Rectus Internus= (Fig. 26, No. B, 2). (Synonym.—Rectus medialis.)

Location.—Inner side of the eyeball.

Origin.—From the supero-anterior border of the optic foramen.

Insertion.—To the sclera on the anterior portion of the eyeball.

Shape.—Thin, fan-shaped.

Relations.—Internally, with the eyeball and with the pyramidalis; externally, with the bony wall of the orbit.

Action.—Pulls the eyeball inward.

THE MUSCLES OF THE EAR

Circumconcha Tensor tympani

=Circumconcha= (Fig. 7, No. 32). Location.—Surrounds the external ear.

Origin and Insertion.—The circumconcha, surrounding the periphery of the ear, is adherent to the skull and loosely to the skin, and is attached to the outer terminus of the supra-occipital crest.

Relations.—Internally, with the skull; externally, with the skin.

Action.—Relaxes the tympanum.

=Tensor Tympani= (Fig. 7, No. 31). Location.—External to the quadrate and to the external auditory meatus.

Origin and Insertion.—From the surface of the quadrate and the inner end of the quadrato-jugal to the inner surface of the tympanum.

Shape.—A few fibers.

Relations.—Internally, with the quadrate and the quadrato-jugal; externally, the integumental duplicature.

Action.—Tenses the tympanum.

FUNCTIONS OF MUSCLES

To cause the feathers on the top of the head to lie flat: Dermo-frontalis. To raise the feathers along the superior part of the neck and along the dorsal region: Dermo-dorsalis.

To tense the patagial region: Dermo-tensor patagii, Dermo-temporalis. To cause the feathers to lie close to the body: Dermo-humeralis, Dermo-pectoralis. To tense the lateral cervical integument: Dermo-temporalis. To support the lingual apparatus and superior larynx: Platysma myoides. To manipulate the feathers and skin of the inferior part of the neck: Cleido-trachealis. To control the skin in the shoulder region: Dermo-spinalis. To cause the feathers of the back to lie close to the skin: Dermo-iliacus. To depress the humeral region: Dermo-ulnaris. To close the jaw: Temporalis, Pterygoideus internus, Pterygoideus externus, Masseter. To open the jaw: Biventer maxilla, Entotympanic. To raise the trachea and hyoid apparatus: Digastricus. To elevate the tongue: Mylo-hyoideus. To pull the tongue to one side: Singly— Cerato-hyoideus, Stylo-hyoideus. Alone when the larynx is fixed— Sterno-hyoideus. Those which protrude the tongue from the mouth: Together— Cerato-hyoideus, Genio-hyoideus. To aid in deglutition: When the base of the tongue is fixed— Sterno-hyoideus. To depress the tongue: Together— Sterno-hyoideus.

To depress the tip of the tongue and elevate the base: Depressor glottis. To elevate the hyoid arches: Cerato-glossus. To extend the head: Complexus, Rectus capitis anticus minor. To flex the head upon the neck: Flexor capitis inferior. To extend the head on the neck and elevate the neck: Biventer cervicis. To raise the neck upward: Longus colli posticus. To flex each vertebra on the preceding or succeeding laterally: Obliquus colli, Intertransversales. To pull the neck downward: Longus colli anterior. To pull the head downward: Together— Rectus capitis lateralis, Trachelo-mastoideus. To pull the head downward and to one side: Singly— Rectus capitis lateralis, Trachelo-mastoideus. To approximate the spinous processes of the vertebræ: Interspinales. To approximate the vertebræ in a supero-lateral direction: Interarticulares. To flex the vertebræ supero-laterally: Obliquo-transversales. To extend the neck: Together when the first rib is fixed— Scalenus medius. To close the glottis: Constrictor glottidis. To open the glottis: Thyreo-arytenoideus. To approximate the tracheal rings: Tracheo-lateralis. To tense the inferior larynx: Broncho-trachealis posticus, Broncho-trachealis anticus, Broncho-trachealis brevis, Bronchialis posticus, Bronchialis anticus.

To relax the inferior larynx: Sterno-trachealis. To aid in respiration: When the first rib is fixed— Intercostales. When wing is fixed— Latissimus dorsi, Dermo-cleido dorsalis. When the scapula is fixed— Serratus magnus anticus, Serratus parvus anticus, Thoraco-scapularis, Levatores costarum, Appendico-costales, Triangularis sterni. To flex the shoulder-joint: Latissimus dorsi. To elevate the humerus: Latissimus dorsi. To draw the scapula forward: Trapezius, Rhomboideus. To close the wing: Teres et infraspinatus. To extend the humerus: Coraco-humeralis, Scapulo-humeralis. To pull the humerus upward and backward: When the scapula is fixed— Supraspinatus. To pull the coracoid outward: Subclavius. To depress the wing: Coraco-brachialis. To depress the scapula: When the ribs are fixed— Thoraco-scapularis. To rotate the humerus: Subscapularis. To flex the forearm: Pronator brevis, Biceps, Brachialis anticus, Anconeus, Tensor patagii longus, Tensor patagii brevis. To extend the arm: Deltoid.

To extend the antibrachial region: Triceps. To raise and to draw the hand forward: Extensor metacarpi radialis longior. To extend the digit: Extensor indicis longus, Extensor digitorum communis, Extensor proprius pollicis, Interosseous dorsalis. To supinate the radial region: Supinator brevis. To flex the hand: Flexor metacarpi radialis. To pronate the forearm: Pronator brevis, Pronator longus. To extend the hand on the forearm: Extensor ossis metacarpi pollicis. To flex the digit: Flexor minimi digiti, Flexor digitorum sublimis, Flexor brevis pollicis, Flexor digitorum profundus, Interosseous palmaris. To flex the hand upon the forearm: Flexor carpi ulnaris, Flexor carpi ulnaris brevior. To rotate the hand toward the body: Flexor carpi ulnaris brevior. To abduct the digits: Abductor minimi digiti. To flex the metacarpus: Flexor metacarpi brevis. To extend the leg: Sartorius. To adduct the thigh: Sartorius, Adductor longus, Adductor magnus. To abduct the thigh: Gluteus primus, Gluteus medius, Gluteus minimus. To pull the thigh forward: Gluteus minimus, Gluteus medius. To extend the leg upon the thigh: Extensor femoris,

Vastus internus. To extend the leg upon the knee: Vastus internus. To flex the leg upon the thigh: Biceps flexor cruris, Semitendinosus, Semitendinosus accessorius, Semimembranosus. To pull the tail down and to one side: Femoro-caudal. To pull the head of the femur backward: Obturator externus. To act as a posterior stay to the head of the femur: Obturator internus. To pull the pelvis forward and to steady it on the head of the femur: Gemellus, Obturator internus, Obturator externus. To extend the metatarsus on the tibia: Gastrocnemius, Soleus, Tibialis posticus. To flex the toes: Peroneus longus, Flexor perforatus medius primus pedis, Flexor perforatus indicis secundus pedis, Flexor perforatus medius secundus pedis, Flexor perforatus indicis primus pedis, Flexor perforans digitorum profundus, Flexor longus hallucis, Flexor perforatus annularis primus pedis. To flex the metatarsus on the tibia: Tibialis anticus. To extend the toes: Extensor longus digitorum, Extensor hallucis brevis. To flex the back laterally and to aid in raising the body. Sacro-lumbalis, Longissimus dorsi. To elevate the tail: Levator coccygis, Levator caudæ. To depress the tail: Depressor caudæ, Infracoccygis. Together— Depressor coccygis, Lateralis caudæ.

To pull the tail downward and to one side: Singly— Lateralis coccygis. Depressor coccygis, Lateralis caudæ. To close the eyelids: Orbicularis palpebrarum. To raise the superior eyelid: Levator palpebræ superioris. To pull the lower eyelid downward: Depressor palpebræ inferioris. To pull the membrana nictitans over the eyeball: Quadratus nictitans, Pyramidalis nictitans. To rotate the eyeball: Obliquus superior, Obliquus inferior. To pull the eyeball upward: Rectus superior. To pull the eyeball downward: Rectus inferior. To pull the eyeball outward: Rectus externus. To pull the eyeball inward: Rectus internus. To tense the ear drum: Tensor tympani. To relax the ear drum: Circumconcha. To depress the humerus: Pectoralis major. To raise the humerus: Pectoralis secundus, Pectoralis tertius.

Footnote 5: