Part 35

_a_, _a′_, Extensor carpi radialis; _b_, extensor carpi obliquus (s. abductor pollicis longus); _c_, _d_, _e_, common or anterior digital extensor; _c′_, _c″_, tendons of insertion of _c_; _d′_, _d″_, tendons of _d_; _e′_, _e″_, tendons of _e_; _f_, tendon of extensor indicis; _g_, extensor digiti quarti; _h_, extensor digiti quinti; _h′_, tendon of _h_; _i_, tendinous, and _k_, fleshy part of flexor carpi externus; _k′_, tendon of _k_; _l_, ulnar head of deep digital flexor; _m_, superficial digital flexor; _n_, brachialis. (After Ellenberger, in Leisering’s Atlas.) ]

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.

[Illustration:

FIG. 228.—MUSCLES OF LEG AND FOOT OF PIG, ANTERO-EXTERNAL VIEW.

_a_, Tibialis anterior; _a′_, tendon of preceding; _b_, peroneus tertius; _b′_, tendon of _b_; _c_, anterior or long digital extensor; _d_, _e_, _f_, _f′_, _f″_, tendons of _c_; _g_, peroneus longus; _g′_, tendon of _g_; _h_, extensor digiti quarti; _h′_, tendon of _h_, which receives _h″_, from the interosseus medius; _i_, extensor digiti quinti; _k_, deep digital flexor; _l_, soleus; _m_, gastrocnemius; _n_, extensor brevis. (After Ellenberger, in Leisering’s Atlas.) ]

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.

THE MUSCLES OF THE DOG

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.

[Illustration:

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.

[Illustration:

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.

[Illustration:

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.

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.

[Illustration:

FIG. 232.—MUSCLES OF THORACIC LIMB OF DOG, INTERNAL VIEW. (Ellenberger-Baum, Anat. des Hundes.) ]

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.

[Illustration:

FIG. 233.—MUSCLES OF ANTIBRACHIUM AND MANUS OF DOG, EXTERNAL VIEW.

_a_, Triceps brachii; _b_, brachialis; _c_, extensor carpi radialis; _d_, common or anterior digital extensor; _d′_, _d″_, _d‴_, _d⁗_, tendons of preceding; _e_, lateral digital extensor; _e′_, _f_, tendons of preceding; _g_, extensor carpi ulnaris; _h_, _h′_, flexor carpi ulnaris; _i_, extensor carpi obliquus (s. abductor pollicis longus); _k_, interossei; _l_, branches from preceding to extensor tendons; _1_, olecranon; _2_, radius; _3_, extensor epicondyle of humerus. (After Ellenberger, in Leisering’s Atlas.) ]

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.

[Illustration:

FIG. 234.—VOLAR MUSCLES OF FORE PAW OF DOG.

_a_, Abductor pollicis brevis et opponens pollicis; _b_, flexor pollicis brevis; _c_, adductor pollicis; _d_, adductor digiti secundi; _e_, adductor digiti quinti; _f_, flexor digiti quinti brevis; _g_, abductor digiti quinti; _h_, interossei; _1_, accessory carpal bone; _2_, first digit; _3–6_, sesamoids of metacarpo-phalangeal joints. (Ellenberger-Baum, Anat. d. Hundes.) ]

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]