A text-book of veterinary anatomy

2. The extensor of the second digit (M. extensor indicis proprius) is covered by the preceding muscle, with which it is partially fused. It arises on the ulna. Its delicate tendon usually unites with the tendon of the middle head of the common extensor which goes to the second digit.

3. The lateral digital extensor (M. extensor digitalis lateralis) consists of two distinct parts: (1) The large dorsal (anterior) muscle (M. extensor digiti quarti proprius) has a long tendon which ends on the fourth digit, and often sends a slip to the fifth digit. (2) The small volar (posterior) muscle (M. extensor digiti quinti proprius) ends by a long tendon on the lateral aspect of the fifth digit.

The supinator has been found by Arloing and Lesbre, but is usually absent in the pig.

The pronator teres is a small muscle which lies on the internal lateral ligament of the elbow. It arises from the internal epicondyle of the humerus, and reaches about to the middle of the inner border of the radius.

The flexor carpi internus is well developed. It arises on the flexor epicondyle of the humerus, and is inserted into the third metacarpal bone.

The flexor carpi medius is narrow and has no ulnar head.

The flexor carpi externus (M. extensor carpi ulnaris) is covered by a thick, tendinous band, which extends from the extensor epicondyle to the accessory carpal bone and outer aspect of the carpus. The tendon of the muscle perforates this band in the distal part of the forearm and ends on the proximal end of the fifth metacarpal bone.

The superficial digital flexor has two bellies. The tendon of the superficial head passes down behind the posterior annular ligament of the carpus (bound down by a special annular ligament), forms a ring at the fetlock for a tendon of the deep flexor, and ends by two branches on the second phalanx of the fourth digit. The tendon of the deep head, after detaching a slip to the tendon of the deep flexor, passes down with the latter (for which it forms a ring), and ends on the third digit.

The deep digital flexor has three heads—humeral, ulnar, and radial. The common tendon divides into four branches, the larger central pair ending on the third phalanges of the principal digits, the smaller pair on the accessory digits. The latter are bound down by a peculiar spiral band. There is no check ligament.

The lumbricales are represented by bundles which extend from the deep flexor tendon to the tendon of the deep head of the superficial flexor.

The third and fourth interossei are present. Each sends two slips to the corresponding sesamoid bones and extensor tendon.

There are flexors, adductors, and abductors of the second and fifth digits.

Muscles of the Pelvic Limb

SUBLUMBAR MUSCLES

The psoas minor is intimately united with the psoas major in front, and has a long small tendon which ends on the psoas tubercle. It has no thoracic part.

The psoas major is large and rounded. It begins at the last rib.

The quadratus lumborum is well developed, and extends forward as far as the twelfth rib.

MUSCLES OF THE HIP AND THIGH

The tensor fasciæ latæ is broad, and its fleshy part reaches almost to the patella.

The gluteus superficialis has a sacral head only; it blends with the biceps femoris.

The gluteus medius has a small lumbar part which does not extend so far forward as in the horse. The deep part (Gluteus accessorius) is pretty clearly marked.

The gluteus profundus is extensive, reaching nearly to the external angle of the ilium.

The biceps femoris has a narrow origin from the sacro-sciatic ligament and tuber ischii. It ends below like that of the ox.

The semitendinosus resembles that of the horse.

The semimembranosus has two insertions as in the ox.

The sartorius has two heads of origin, between which the external iliac vessels are situated. The inner arises from the tendon of the psoas minor, the outer one from the iliac fascia.

The graciles are united at their origin even more than in the ox.

The pectineus is well developed and is flattened from before backward.

The adductor shows no division and is partially fused with the gracilis. It ends on the femur just above the origin of the gastrocnemius.

The quadratus femoris is large.

The obturator externus resembles that of the horse.

The obturator internus is extensive and strong; its tendon emerges through the obturator foramen.

The gemellus is fused in part with the obturator internus.

The quadriceps femoris is more clearly divided than in the horse, and its action is transmitted by a single patellar ligament.

The capsularis is absent.

MUSCLES OF THE LEG AND FOOT

The peroneus tertius resembles that of the ox, but its tendon is not perforated by that of the tibialis anterior, and ends on the inner (second) large metatarsal bone, detaching a strong branch to the first and second tarsal bones.

The tibialis anterior arises on the tibial crest. Its tendon passes over the hock along the inner border of the tendon of the peroneus tertius (both being bound down by an annular ligament), and is inserted into the inner (second) metatarsal and first tarsal bones.

The peroneus longus lies partly on the outer surface of the peroneus tertius. Its tendon crosses those of the lateral extensor, passes along a groove on the plantar surface of the fourth tarsal bone, and ends on the first tarsal and second metatarsal bones.

The anterior or long digital extensor arises with the peroneus tertius and is largely covered by it and the peroneus longus. It divides into three parts. The tendon of the inner division (M. extensor digiti tertii) ends on the inner chief (third) digit; that of the middle division by two branches on the principal digits; and that of the outer division by three branches on the second, fourth, and fifth digits.

The lateral digital extensor divides into proper extensors of the fourth and fifth digits (Extensores digiti quarti et quinti).

The extensor hallucis longus arises on the fibula and ends on the inner small (second) digit.

The extensor digitalis brevis is well developed and consists of three parts. The inner and outer tendons end on the first phalanges of the chief digits, the middle one joins the common extensor tendon of the same.

The gastrocnemius presents nothing special.

The soleus is wide, and is partly blended with the external head of the gastrocnemius.

The superficial digital flexor has a large belly. Its tendon ends on the two chief digits, and is also connected with the ligaments of the accessory digits.

The inner head of the deep digital flexor (flexor digitalis longus) is relatively small. The common tendon ends as in the thoracic limb.

The popliteus presents no special features.

The plantar muscles resemble their homologues of the fore limb, except that the adductors of the accessory digits and the lumbricales are absent.

Muscles of the Face

The panniculus carnosus is well developed and presents two distinct bands, one of which is inserted into the lower lip, the other into the scutiform cartilage of the ear.

The orbicularis oris is poorly developed. In the upper lip it is divided centrally, and in the lower it is distinct only near the angles of the mouth.

The levator nasolabialis is wide and undivided, and ends in the upper lip.

The levator labii superioris proprius arises behind the infraorbital foramen, runs forward under the preceding muscle, and ends in numerous small tendons around the nostril, some blending with those of the opposite side.

The zygomaticus, long and narrow, arises on the scutiform cartilage, and ends at the angle of the mouth.

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.

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.

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.

The deltoid is clearly divided into scapular and acromial parts, the former arising on the spine, the latter on the acromion of the scapula. Both end on the deltoid tuberosity.

The supraspinatus ends chiefly on the external tuberosity of the humerus, but has a small attachment to the internal tuberosity also.

The infraspinatus is inserted into the outer surface of the external tuberosity of the humerus.

The teres minor arises on a tubercle on the posterior border of the scapula, just above the glenoid cavity, and is inserted into the deltoid ridge.

The subscapularis is wide and is somewhat multipennate in structure, being intersected by fibrous septa which are attached to the rough lines on the costal surface of the scapula.

The teres major is thick. It arises on the upper part of the posterior border of the scapula and on the subscapularis.

The coraco-brachialis is short and undivided, and is inserted into the upper part of the postero-internal surface of the humerus.

The capsularis is absent.

The biceps brachii lies almost entirely on the inner surface of the humerus. It is long and fusiform. The tendon of origin is round, and passes through the capsule of the shoulder joint. The tendon of insertion is bifid, one branch being attached to the ulnar, the other to the radial tuberosity.

The brachialis is very little curved, and is inserted chiefly into the tuberosity and inner border of the ulna.

The tensor fasciæ antibrachii is thin and narrow. It arises on the outer surface of the latissimus dorsi, and ends on the olecranon and the fascia of the forearm.

The triceps has an additional deep head (Caput accessorium), which arises just below the head of the humerus.

The brachio-radialis is a long, narrow, delicate muscle, situated superficially on the anterior surface of the forearm. It arises with the extensor carpi on the crest above the extensor epicondyle of the humerus, and is inserted into the distal part of the inner border of the radius. It is often much reduced, and is sometimes absent. It rotates the forearm and paw outward.

The extensor carpi divides into two parts. The larger outer part, the extensor carpi radialis brevis, ends on the proximal end of the third metacarpal bone. The inner and more superficial part, the extensor carpi radialis longus, ends on the second metacarpal bone. (A tendon to the fourth metacarpal may occur.)

The extensor carpi obliquus or abductor pollicis longus arises from the outer border and anterior surface of the ulna, the interosseous ligament, and the outer border of the radius. It is inserted into the first metacarpal bone by a tendon which contains a small (sesamoid?) bone. It abducts the first digit.

There are three (or four) extensors of the digits.

1. The common digital extensor (M. extensor digitalis communis) arises on the extensor epicondyle of the humerus and the lateral ligament of the elbow joint. It has four bellies, each terminating in a tendon. These are inserted into the third phalanges of the second, third, fourth, and fifth digits.

2. The extensor of the first and second digits (M. extensor pollicis longus et extensor indicis proprius) is small, and is covered by the common and lateral extensors. It arises on the proximal part of the ulna. Its tendon passes down with that of the common extensor and divides into two branches. The delicate inner branch ends on the first digit, while the other blends with the tendon of the common extensor for the second digit.

3. The lateral digital extensor (M. extensor digitalis lateralis) consists of two muscles which are not rarely fused. They arise on the extensor epicondyle of the humerus and the lateral ligament of the elbow joint. The larger, superficial belly (M. extensor digiti tertii et quarti) terminates on a tendon which divides at or near the carpus into two branches, which are inserted into the third phalanges of the third and fourth digits, blending with the corresponding tendons of the common extensor. The posterior belly (M. extensor digiti quinti) terminates by a tendon which fuses with that of the common extensor for the fifth digit.

The ulnaris lateralis or extensor carpi ulnaris corresponds to the flexor carpi externus of the horse, but is an extensor of the carpus. It is a large flat muscle which lies on the outer surface of the ulna. It arises on the extensor epicondyle of the humerus, and is inserted into the proximal end of the fifth metacarpal and the accessory carpal bone.

The ulnaris medialis or flexor carpi medius (s. ulnaris) consists of two quite distinct heads. The larger, humeral head arises on the flexor epicondyle, while the smaller, superficial ulnar head arises on the posterior border of the ulna. The tendons of the two end together on the accessory carpal bone.

The radialis volaris or flexor carpi internus (s. radialis) arises on the flexor epicondyle of the humerus and is inserted by a bifid tendon into the second and third metacarpal bones.

The tendons of the foregoing muscles are provided with synovial sheaths at the carpus.

The pronator teres is a round muscle, which is situated superficially on the inner border of the proximal part of the radius. It arises on the flexor epicondyle of the humerus, and is inserted into the internal border of the radius. Its action is to flex the elbow and rotate the forearm inward.

The superficial digital flexor is situated superficially on the posterior and inner surfaces of the forearm. It arises on the flexor epicondyle of the humerus and terminates near the carpus on a tendon which passes downward outside of the carpal canal and receives below the carpus two reinforcing bands, one from the accessory carpal, the other from the sesamoid bone at the inner side of the carpus. Below this it divides into four branches, which are inserted into the second phalanges of the second, third, fourth, and fifth digits.

The deep digital flexor has humeral, ulnar, and radial heads, the latter arising from the inner border of the radius. They unite on a common tendon which passes down through the carpal canal, gives off a branch to the first digit, and divides into four branches. These perforate the tendons of the superficial flexor and are inserted into the third phalanges of the second to the fifth digits. The tendons are provided with synovial sheaths from the middle of the metacarpus downward, and are held in place by three digital annular ligaments.

The palmaris longus accessorius (?) is a small muscle which arises from the deep flexor below the middle of the forearm and ends by two tendons which unite with those of the superficial flexor for the third and fourth digits.

The supinator is a short, wide muscle which arises on the humerus beneath the external lateral ligament, crosses the anterior surface of the radius, and is inserted into the inner border of the radius. (A pouch of the capsule of the elbow joint lies under the tendon of origin.) Its action is to rotate the forearm outward (supination).

The pronator quadratus consists of fibers which cross the inner surface of the interosseous ligament of the forearm, except at the two extremities of the latter. It is attached to the inner border of the ulna and the anterior surface of the radius. It rotates the forearm inward (pronation).

The palmaris brevis (?) is a very small muscle, which arises on the tendon of the superficial digital flexor for the fifth digit, and is inserted at the fifth metacarpo-phalangeal joint into the sheath and annular ligament of the deep flexor.

The lumbricales are three very delicate muscles, which arise on the tendons of the deep flexor, and are inserted into the first phalanges of the third, fourth, and fifth digits.

The abductor pollicis brevis et opponens pollicis, a very small pale muscle, arises on the fibrous band which connects the superficial flexor tendon with the inner carpal sesamoid, and ends on the distal end of the first metacarpal bone and the first phalanx of the first digit. It abducts the first digit.^[76]

The flexor pollicis brevis arises on the posterior carpal ligament over the second metacarpal bone, and ends on the volar sesamoid of the first digit.

The adductor pollicis, situated externally to the preceding, is the largest of the thumb muscles. It arises between the preceding and the second interosseous muscle, and is inserted into the first phalanx of the first digit.

The adductor digiti secundi is situated between the second interosseous muscle and the adductor digiti quinti. It arises on the carpal ligament, and ends on the first phalanx of the second digit.

The adductor digiti quinti arises close to the preceding muscle, and passes outward to end on the first phalanx of the fifth digit.

The flexor digiti quinti arises on the ligament connecting the accessory carpal to the third and fourth metacarpal bones, crosses the corresponding interosseous muscle, and ends on the fifth digit with the next muscle.

The abductor digiti quinti is larger than the two preceding muscles; it arises on the accessory carpal bone, and ends on the outer sesamoid of the fifth digit and on the lateral ligament.

There are four interossei which lie on the volar (posterior) surface of the metacarpus. They are well developed and fleshy. They arise on the distal row of the carpus and on the proximal ends of the metacarpals. Each divides distally into two branches, which are inserted by small tendons on the corresponding sesamoid bones, and detach slips to the extensor tendons.

Muscles of the Neck

The sterno-cephalicus is well developed. It arises on the manubrium sterni and ends on the mastoid process, blending with the cleido-cervicalis.

The scalenus ventralis (s. primæ costæ) arises on the last four cervical transverse processes, and is inserted into the first rib.

The scalenus dorsalis (s. supracostalis) is large. Anteriorly it blends with the preceding muscle, while posteriorly it divides into two parts. The upper part is inserted on the third and fourth ribs, the lower part by a long, thin tendon on the eighth rib.

The longus colli resembles that of the horse.

The rectus capitis anterior major arises on the transverse processes of the second to the sixth cervical vertebræ and ends as in the horse. The rectus minor and lateralis resemble those of the horse.

The intertransversales resemble those of the ox.

The splenius is strong and extensive. It arises on the first four or five thoracic spines and the median raphé of the neck, and is inserted into the occipital crest and mastoid process.

The complexus is composed of two parts—the biventer cervicis and the complexus major proper. The biventer cervicis arises from the transverse processes of the fifth and sixth, and the spines of the second to the fifth (or sixth) thoracic vertebræ, from the ligamentum nuchæ, and the median raphé. It has four tendinous intersections. The complexus major arises on the transverse processes of the first three or four thoracic vertebræ and the articular processes of the last five cervical. Both end on a strong common tendon which is inserted into the occipital crest and the depression below it.

The trachelo-mastoideus consists of two unequal portions. The large dorsal part (M. longissimus capitis) arises on the transverse processes of the first four thoracic and the articular process of the last three or four cervical vertebræ, and ends with the splenius on the mastoid process of the temporal bone. The small ventral part (M. longissimus atlantis) arises on the articular processes of the third, fourth, and fifth cervical vertebræ, and ends on the wing of the atlas.

The other muscles present no striking differential features, but it may be noted that distinct interspinales are present.

Muscles of the Thorax

There are twelve pairs of levatores costarum.

The external intercostals do not occupy the spaces between the costal cartilages.

The diaphragm has a small tendinous center. The œsophageal opening is between the pillars. The fleshy rim is attached at the costo-chondral junctions from the eighth backward, and along the thirteenth rib nearly its entire length.

Muscles of the Back and Loins

The serratus anticus arises from the median raphé of the neck and the first six or seven thoracic spines, and is inserted into the second to the ninth ribs. It is well developed. The serratus posticus—much weaker—arises on the lumbo-dorsal fascia, and is inserted into the last three or four ribs. Thus one or two ribs intervene between the two.

The transversalis costarum (Iliocostalis) is well developed, and extends from the ilium to the sixth, fifth, or fourth cervical vertebra.

The longissimus resembles that of the other animals, but the spinalis et semispinalis separates clearly at the sixth or seventh thoracic vertebra. It is inserted into the articular and spinous processes of the last six cervical vertebræ. It has no depression in the lumbar region for the gluteus medius.

The intertransversales are fleshy, as in the ox.

The interspinales are distinct, especially in the lumbar region.

Muscles of the Tail

These present the same general arrangement as in the horse. The sacro-coccygei, however, arise on the lumbar vertebræ also, and the coccygeus on the ischiatic spine. There is found a sacro-coccygeus accessorius, which arises on the internal border of the ilium, the edge of the sacrum, and the transverse processes of the first coccygeal vertebræ, and is inserted between the superior and lateral sacro-coccygei. It is homologous with the intertransversales.

The abdominal tunic is practically absent.

The obliquus abdominis externus has an extensive fleshy portion. It arises from the last eight or nine ribs and the lumbo-dorsal fascia.

The obliquus abdominis internus arises from the external angle of the ilium and the lumbo-dorsal fascia. The fibers have an almost vertical direction, and there is a fleshy attachment to the last rib.

The rectus abdominis is attached by a long tendon on the first five or six costal cartilages, and by fleshy fibers on the xiphoid cartilage. It has three to six indistinct tendinous inscriptions.

The transversus abdominis presents no special features except that the posterior part of its aponeurosis splits into two layers which include the rectus between them.

Muscles of the Pelvic Limb

The psoas minor arises on the last thoracic and first four or five lumbar vertebræ, and is inserted into the ilio-pectineal line.

The psoas major is short, arising from the last four lumbar vertebræ.

The outer head of the iliacus is small, while the inner head is large and fuses with the psoas major.

The quadratus lumborum is well developed, and extends laterally beyond the outer edge of the ilio-psoas. It arises from the last four ribs and the lumbar transverse processes, and ends on the pelvic surface of the wing of the ilium.

The tensor fasciæ latæ consists of two parts. The anterior part is long and rounded; the posterior is shorter and fan-like.

The gluteus superficialis is small. It arises on the sacrum, first coccygeal vertebræ, and sacro-sciatic ligament. It is inserted below and behind the trochanter major of the femur, on the outer branch of the linea aspera.

The gluteus medius has no lumbar portion. It is inserted into the trochanter major by a strong tendon.

The gluteus profundus is broad and fan-shaped. It arises on the superior ischiatic spine and on the ilium as far forward as the gluteal line, and is inserted into the trochanter major below the medius.

The pyriformis is not blended with the gluteus medius. It arises from the border of the sacrum and from the sacro-sciatic ligament, and ends on the trochanter major.

The biceps femoris has two heads of origin which soon fuse. The larger head arises from the sacro-sciatic ligament and tuber ischii, the smaller one from the tuber ischii. The aponeurosis of insertion ends on the patella, the patellar ligament, and the tibial crest. There is also a tendinous band, which comes from the deep face of the muscle and terminates at the tarsus, as in the horse.

The abductor cruris posterior may be regarded as an accessory head of the biceps femoris. It is a thin, muscular band which arises on the sacro-sciatic ligament, passes downward between the biceps and semimembranosus, and ends by blending with the former.

The semitendinosus arises from the tuber ischii only. It ends as in the horse.