Chapter V: Muscles of the Leg and Foot (1)

There are four =digital extensors=, two of which are fused with each other and the peroneus tertius in the upper third of the leg.

1. The =anterior= or =long digital extensor= (M. extensor digitalis longus) arises by the common tendon in the extensor fossa of the femur, and separates from the other muscles near the middle of the leg. At the distal end of the tibia it terminates on a tendon which passes down over the hock (bound down by two annular ligaments) and ends like that of the thoracic limb.

FIG. 223.—MUSCLES OF LEG AND FOOT OF OX, INNER VIEW.

_a_, Peroneus tertius; _b′_, tendon of anterior or long extensor; _e_,
deep digital flexor; _e′_, tendon of _e_; _e″_, branch of _h_ to
superficial flexor tendon; _f_, gastrocnemius; _g_, tendon of
superficial digital flexor; _h_, interosseus medius or suspensory
ligament; _i_, annular ligaments; _l_, branch of _h_; _m_, long
digital flexor; _o_, popliteus; _20_, patella; _28_, tuberosity of
tibia. (After Ellenberger-Baum, Anat. für Künstler.)
]

2. The =internal digital extensor= (M. extensor digiti tertii proprius) arises in common with the preceding muscle and the peroneus tertius, and is covered by them to the distal third of the tibia. Its tendon passes under the annular ligaments between those of its cogeners and ends on the second phalanx of the inner digit.

3. The =lateral digital extensor= (M. extensor digitalis lateralis s. digiti quarti proprius) arises on the external lateral ligament of the stifle joint and the external condyle of the tibia. Its tendon passes over the outer surface of the hock, and terminates on the anterior surface of the second phalanx of the external digit.

The reinforcing bands from the suspensory ligament are arranged as in the fore limb.

4. The =extensor brevis= resembles that of the horse, but is inserted on the tendon of the anterior extensor only.

The =peroneus longus= (not present in the horse) is situated in front of the lateral extensor. It arises on the external condyle of the tibia and the fibrous band which represents the shaft of the fibula. Its tendon passes downward and backward over the outer surface of the hock, crosses over that of the lateral extensor and under the lateral ligament, and ends on the first tarsal bone (Cuneiform parvum). It is enveloped by a synovial sheath. It would apparently act as an inward rotator at the hock joint.

FIG. 224.—DISTAL PART OF LIMB OF OX WITH SYNOVIAL SHEATHS AND BURSÆ
INJECTED, ANTERIOR VIEW.

_1_, Tendon of extensor digiti tertii, with bursa (_1′_); _2_, tendon
of anterior extensor; _2′_, branch of _2_, with synovial sheath
(_2″_); _3_, tendon of extensor digiti quarti, with bursa (_3′_);
_a_, metatarsus; _b_, first phalanx; _c_, second phalanx. (After
Schmidtchen.)
]

FIG. 225.—DISTAL PART OF LIMB OF OX WITH SYNOVIAL SHEATHS INJECTED,
POSTERIOR VIEW.

_1_, Superficial flexor tendon; _1′_, _1′_, branches of _1_; _1″_,
_1‴_, upper part of synovial sheaths of _1′_, _1′_; _2_, deep flexor
tendon; _2′_, _2″_, branches of _2_; _2″_, upper part of synovial
sheath of _2′_; _3_, _3_, lateral branches of interosseus medius or
suspensory ligament; _3′_, branch of same to superficial flexor
tendon; _a_, fetlock joint; _b_, pastern joint; _c_, coffin joint;
_d_, _e_, annular ligaments; _f_, crucial interdigital ligament.
(After Schmidtchen.)
]

The =peroneus tertius= is a well-developed muscle which arises on the common tendon with the long and internal extensors. It has a large, fusiform belly, which is superficially situated on the front of the leg. Close to the tarsus it ends on a flat tendon, which is perforated by that of the tibialis anterior, and ends on the large metatarsal and second and third (fused) tarsal bones (Cuneiform magnum).

The =tibialis anterior= is smaller, and arises by two heads. The larger head springs from the outer surface of the tuberosity of the tibia; the outer, smaller one (M. extensor hallucis longus), from the upper part of the external border of the tibia and the fibrous band which replaces the shaft of the fibula. The tendon perforates that of the preceding muscle and ends on the metatarsal and second and third tarsal bones.

B. POSTERIOR GROUP

The =gastrocnemius= and =soleus= resemble those of the horse. The =superficial flexor= is more fleshy than in the horse. Its tendon terminates as in the fore limb.

The =deep flexor= has in its upper part a close resemblance to that of the horse, but the superficial head (tibialis posterior) is larger and distinct. The tendon ends like that on the fore limb.

MUSCLES OF THE PIG

MUSCLES OF HEAD

The =facial panniculus= is pale, thin, and difficult to separate from the skin.

The =orbicularis oris= is little developed.

The =levator nasolabialis= is thin and pale, and is undivided.

The =levator labii superioris proprius= may well be termed the =levator rostri=. It has a large penniform belly, which arises in the fossa on the lacrimal bone and maxilla. The tendon ends on the anterior part of the os rostri. A muscular slip connects it with the premaxilla.

The =zygomaticus= arises on the fascia over the masseter and ends at the angle of the mouth.

The =depressor labii inferioris= separates from the buccinator only near the angle of the mouth; it ends by a number of tendinous branches in the lower lip.

The =dilatator naris lateralis= is well developed. It arises under the levator rostri and ends by a tendinous network around the nostril.

The =dilatator naris transversus= is represented only by a few fibers which cross over the os rostri.

The =depressor rostri= arises on the facial crest. It has a long strong tendon which passes below the nostril and turns up and inward to meet the tendon of the opposite side and end in the skin of the snout. It depresses the snout and contracts the nostril.

The malaris is absent, and the other palpebral muscles present no special features.

MUSCLES OF MASTICATION

The =digastricus= has only one belly. It ends on the inner and lower surface of the mandible, in front of the groove for the facial vessels.

The other muscles have no important differential features.

The same is true of the oral hyoid muscles.

MUSCLES OF THE NECK

The =panniculus carnosus= consists of two layers which cross each other obliquely. The fibers of the superficial layer are directed nearly vertically, those of the deep layer toward the face, on which they are continued to form the facial portion.

The =mastoido-humeralis= is described on p. 314.

The =sterno-cephalicus= (Sterno-mastoideus) arises on the sternum and is inserted by a long round tendon on the mastoid process.

The thyroid portion of the =sterno-thyro-hyoideus= has a peculiar arrangement. It arises (separately from the opposite muscle) on the manubrium sterni. About the middle of the neck it has an oblique tendinous intersection, beyond which it divides into two branches; one of these is inserted in the usual fashion, the other ends on the laryngeal prominence. The hyoid portion is well developed.

The =omo-hyoideus= is thin. It arises as in the horse, but has no connection with the mastoido-humeralis nor with the opposite muscle.

The =omo-transversarius= arises on the first or second cervical vertebra (under cover of the mastoido-humeralis), and is inserted into the lower part of the scapular spine.

There are two =scaleni=. The =scalenus ventralis= (s. primæ costæ) resembles that of the ox, is attached to the last four cervical vertebræ, and is perforated by the nerves of the brachial plexus. The =scalenus dorsalis= (s. supracostalis) arises on the transverse processes of the third to the sixth cervical vertebra, and ends on the third rib.

FIG. 226.—SUPERFICIAL MUSCLES OF PIG, AFTER REMOVAL OF PANNICULUS
CARNOSUS.

_a_, Levator nasolabialis; _b_, levator labii superioris proprius;
_b′_, fleshy slip of _b_ which comes from premaxilla; _c_,
dilatator naris lateralis; _d_, depressor rostri; _e_, orbicularis
oris; _f_, depressor labii inferioris; _g_, zygomaticus; _h_,
masseter; _i_, _i′_, _i″_, brachiocephalicus (cleido-occipitalis,
cleido-mastoideus, pars clavicularis); _k_, sterno-cephalicus;
_l_, sterno-hyoideus; _m_, omo-transversarius; _n_, _n′_,
trapezius; _o_, anterior deep pectoral; _p_, latissimus dorsi;
_q_, lumbo-dorsal fascia; _r_, obliquus abdominis externus; _r′_,
aponeurosis of _r_; _s_, serratus posticus; _t_, serratus magnus;
_u_, posterior deep pectoral; _v_, supraspinatus; _w_, _w′_,
deltoideus; _x_, long head of triceps; _y_, external head of
triceps; _z_, tensor fasciæ antibrachii; _1_, brachialis; _2_,
extensor carpi radialis; _3_, extensor digiti quarti; _4_,
extensor digiti quinti; _5_, extensor carpi ulnaris; _6_, ulnar
head of deep flexor; _7_, gluteus medius; _8_, tensor fasciæ latæ;
_9_, _10_, _10′_, biceps femoris; _11_, semitendinosus; _12_,
semimembranosus; _13_, caudal muscles; _14_, panniculus adiposus
in section. (After Ellenberger, in Leisering’s Atlas.)
]

The =straight muscles= of the head present no special features.

The =longus colli= is separated from the opposite muscle, so that part of the bodies of the cervical vertebræ is exposed as in man.

The =intertransversales= resemble those of the ox.

The =splenius= is thick and extensive. It ends in three parts on the occipital, the temporal, and the wing of the atlas (inconstant).

The =trachelo-mastoideus= is small, and its atlantal portion is blended with the longissimus.

The =complexus= is large, and is clearly divided into two portions: the dorsal portion (Biventer cervicis) is marked by several tendinous intersections; the ventral part is the complexus proper.

The =obliquus capitis posterior= is relatively thin.

The =recti capitis= are thick and more or less fused.

MUSCLES OF THE THORAX

The =levatores costarum= and =rectus thoracis= present no special features.

The =external intercostal= muscles are absent under the serratus anticus and posticus and the digitations of the external oblique.

The =internal intercostals= are thick between the cartilages of the sternal ribs.

The =retractor costæ= and the =transversus thoracis= resemble those of the horse; the latter extends back to the eighth cartilage and fuses with the transversus abdominis.

The =diaphragm= has seven costal digitations on each side, the posterior ones being attached to the ribs at some distance (ca. one-third to one-fourth of rib-length) from the costo-chondral junction. The line of attachment reaches the latter at the tenth rib, and passes along the eighth cartilage to the xiphoid process. The tendinous center is more rounded than in the horse. The crura are well developed. The right crus is very large, and is perforated by the extensive slit-like opening for the œsophagus, which is median in position, and lies about two and one-half to three inches (ca. 6 to 8 cm.) below the twelfth thoracic vertebra. The hiatus aorticus is between the crura.

ABDOMINAL MUSCLES

The =abdominal tunic= is little developed.

The =obliquus abdominis externus= has an extensive fleshy portion and a correspondingly narrow aponeurosis; the latter does not detach a femoral lamina, but is reflected in toto to form the inguinal (Poupart’s) ligament.

The =obliquus abdominis internus= resembles that of the ox; a small fusiform muscle, which crosses the inguinal canal obliquely and is attached on the abdominal surface of the inguinal ligament, is apparently a detached slip of the internal oblique.

The =rectus abdominis= is extensive and thick. It has seven to ten intersections. Its tendon of insertion fuses largely with the common tendon of the gracilis, and does not give off an accessory band to the head of the femur.

The fleshy part of the =transversus abdominis= is well developed. It blends in front with the transversus thoracis.

The =cremaster externus= is present in the female as well as in the male.

MUSCLES OF THE BACK AND LOINS

The =serratus anticus= is inserted into the fifth to the eighth ribs inclusive, the serratus posticus into the last four or five ribs. There are usually no digitations attached to the ninth and tenth ribs.

The =transversalis costarum= (Iliocostalis) extends to the wing of the atlas.

The =spinalis et semispinalis= can be separated without much difficulty from the longissimus dorsi, the division from the common mass of the loins beginning about the first lumbar vertebra.

The =multifidus= resembles that of the horse.

=Interspinales= are present, as well as distinct =intertransversales= of the back and loins.

MUSCLES OF THE TAIL

The superior and lateral =sacro-coccygei= arise as far forward as the last lumbar vertebra. Gurlt explains the twist of the tail as being due to the spiral arrangement of the insertions of the tendons.

MUSCLES OF THE THORACIC LIMB

MUSCLES OF THE SHOULDER GIRDLE

The =trapezius= is very wide, its line of origin extending from the occipital bone to the tenth thoracic vertebra. There is no clear division between its two parts, which are both inserted into the scapular spine.

The =omo-transversarius= resembles that of the ox.

The =rhomboideus= consists of three portions. The =cervical portion= (Rhomboideus cervicalis) is greatly developed, its origin extending from the second cervical to the sixth thoracic vertebra. The =cephalic portion= (Rhomboideus capitis) arises with the splenius on the occipital bone, and is inserted with the cervical part. The =dorsal portion= (Rhomboideus thoracalis) extends as far back as the ninth or tenth thoracic vertebra.

The =latissimus dorsi= is attached to the four ribs preceding the last. It is inserted into the internal lip of the bicipital groove.

The =mastoido-humeralis= divides into two parts, the =cleido-mastoideus= and =cleido-occipitalis=, which arise on the mastoid process and occipital crest respectively, and unite at the fibrous vestige of the clavicle.

The =anterior superficial pectoral= is thin. The =posterior superficial pectoral= is divided into parts, one of which ends on the humerus, the other on the fascia of the forearm.

The =deep pectoral= is clearly divided into two parts. The =scapular portion= resembles that of the horse, but its origin does not extend behind the first two chondro-sternal joints. The =posterior deep pectoral= is very long.

The cervical portion of the =serratus magnus= is greatly developed, its origin extending from the wing of the atlas to the upper part of the fifth rib, and passing under the thoracic portion; the latter resembles that of the ox.

MUSCLES OF THE SHOULDER

The =deltoid= is undivided; it arises from the aponeurosis covering the infraspinatus, and it ends largely on the deltoid ridge, but partly on the fascia of the arm.

The =supraspinatus= is large; it ends chiefly on the external tuberosity of the humerus.

The =infraspinatus= is inserted into a depression below the posterior division of the external tuberosity.

The =teres minor= is well developed; it ends on a tubercle between the external and deltoid tuberosities of the humerus.

The =subscapularis= and =teres major= have no remarkable features.

The =coraco-brachialis= is short and undivided.

The =capsularis= is very small and frequently absent.

MUSCLES OF THE ARM

The =biceps brachii= is fusiform and not greatly developed. Its tendon of origin is rounded and passes through the capsule of the shoulder joint. The tendon of insertion is bifid, ending on the radius and ulna.

The =brachialis= is well developed, and also ends on the radius and ulna.

The =tensor fascias antibrachii= resembles that of the horse.

The =long head of the triceps= is divided into two parts, except at its distal end, under which there is a synovial bursa. The =external head= is inserted into a crest on the outer surface of the olecranon by a thin tendon, under which there is a bursa. The =internal head= arises near the head of the humerus, beneath the coraco-brachialis.

There are two =anconei=.

MUSCLES OF THE FOREARM AND DIGITS

The =extensor carpi radialis= is a strong, fleshy muscle, the tendon of which is inserted into the proximal end of the third metacarpal bone. It may be divided into two parts (M. extensor carpi radialis longus, brevis).

The =extensor carpi obliquus= is well developed; it ends on the second metacarpal bone.

There are three (or four) =digital extensors=.

1. The =common= or =anterior digital extensor= (M. extensor digitalis communis) arises on the extensor epicondyle of the humerus and the lateral ligament of the elbow, and divides into three parts. The tendon of the =inner part= divides into two branches which end on the =second= and =third digits=; the tendon to the second digit is small and often absent. The tendon of the =middle part= divides lower down into two branches for the =third= and =fourth= (chief) =digits=; above this bifurcation it detaches a small branch to the =second digit=, which usually unites with the tendon of the extensor indicis. The tendon of the =deep head= divides into two branches, the inner one joining the tendon of the middle head, while the outer one ends on the =fifth digit=.

FIG. 227.—MUSCLES OF ANTIBRACHIUM AND MANUS OF PIG, ANTERO-EXTERNAL
VIEW.

_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.

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.

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.

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.

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.

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.

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]

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.

MUSCLES OF THE ABDOMEN

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

FIG. 235.—MUSCLES OF TAIL, ANUS, AND GENITAL ORGANS OF DOG.

_1_, Ilium; _2_, femur; _3_, tuber ischii; _4_, sacro-sciatic lig.;
_5_, sacral region; _6_, tail; _7_, penis; _8_, anus; _9_, rectum;
_a_, sacro-coccygeus superior; _b_, sacro-coccygeus accessorius;
_c_, coccygeus; _d_, sacro-coccygeus inferior; _e_, retractor ani;
_f_, _f′_, sphincter ani externus; _g_, retractor penis; _h_,
bulbo-cavernosus; _i_, transversus perinei (?); _k_, _m_,
ischio-urethrales; _l_, ischio-cavernosus; _n_, tendon of obturator
internus; _o_, gemellus; _p_, urethral muscle. (After Ellenberger,
in Leisering’s Atlas.)
]

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.

FIG. 236.—MUSCLES OF PELVIC LIMB OF DOG, INTERNAL VIEW.

_a_, Ilio-psoas; _b_, tendon of psoas minor; _c_, sacro-coccygeus
ventralis lateralis; _d_, coccygeus; _e_, pyriformis; _f_, obturator
internus; _g_, origin of retractor ani; _h_, _h′_, sartorius; _i_,
rectus femoris; _k_, vastus internus; _l_, pectineus; _m_, adductor;
_n_, gracilis; _o_, semitendinosus; _p_, semimembranosus; _q_,
gastrocnemius, inner head; _q′_, tendon of gastrocnemius; _r_,
superficial digital flexor; _r′_, tendon of _r_; _s_, tarsal tendon
of biceps femoris; _t_, popliteus; _u_, deep digital flexor, outer
head (flexor hallucis longus); _u′_, long digital flexor; _u″_,
common tendon of u and _u′_; _v_, tendon of tibialis posterior; _w_,
tibialis anterior; _x_, tendon of anterior or long digital extensor;
_1_, pelvic surface of ilium; _2_, section of symphysis pelvis; _3_,
tuber ischii; _4_, internal condyle of femur; _5_, ligamentum
patellæ; _6_, _7_, internal surface of tibia; _8_, tarsus; _8′_,
fibular tarsal bone; _9_, metatarsus. (Ellenberger-Baum, Anat. d.
Hundes.)
]

The =semimembranosus= is large and arises from the ischium only. It divides into two portions: the anterior portion ends on the tendon of the pectineus, on the femur above the internal condyle, and on the inner (Vesalian) sesamoid bone; the posterior portion ends on the internal condyle of the tibia, the tendon passing under the internal lateral ligament of the stifle joint.

The =rectus femoris= has only one tendon of origin. The single patellar ligament acts as the tendon of insertion of the quadriceps.

The =capsularis= is usually present, but is small and pale.

The =sartorius= consists of two portions. It arises from the external angle and border of the ilium. The anterior portion ends on the patella, the posterior on the internal surface of the tibia, its tendon blending with that of the gracilis.

The =graciles= are not so much fused at their origin as in the other animals.

The =pectineus= is long and slender. It arises from the ilio-pectineal eminence and ends on the internal branch of the linea aspera above the distal end of the femur.

There are two distinct =adductors=. The small anterior one ends on the proximal third of the femur, the posterior one on the distal part of the femur and on the inner face of the stifle joint.

The =quadratus femoris= is short and strong. The other external rotators of the thigh present no special features.

The =peroneus tertius= is represented by a tendinous band which arises on the internal surface of the tibia below the crest. It passes downward on the inner surface of the tibialis anterior, blends with the annular ligament above the tarsus, and is attached to the joint capsule and the proximal end of the third metatarsal bone.

Arloing and Lesbre say: “The third peroneus is a proper extensor of
the fifth digit; it is a very feeble, fleshy band, situated behind the
peroneus brevis, which it partially covers. It is attached to the
upper part of the fibula, and is continued by a long, delicate tendon
which passes in the same malleolar groove with the muscle mentioned;
it then crosses behind the tendon of the peroneus longus and extends
to the phalanges of the outer digit, where it joins one of the
branches of the common extensor.”

The =tibialis anterior= is large and superficial. It arises on the external condyle and crest of the tibia, and is inserted into the first metatarsal bone, or into the first tarsal and second metatarsal.

There are four =extensors of the digits=.

1. The =anterior= or =long digital extensor= (M. extensor digitalis longus) is fusiform, and lies largely under the preceding muscle. It arises from the extensor fossa of the femur. The tendon is bound down by two annular ligaments, and divides below the tarsus into four branches, which end on the distal phalanges of the digits (second to fifth).

2. The =lateral digital extensor= (M. extensor digitalis lateralis) is feeble and semipennate. It arises on the fibula below the head. The tendon passes under the lateral ligament of the tarsus and joins the branch of the tendon of the long extensor for the fifth digit.

3. The =extensor hallucis longus= is a very thin muscle which arises from the fibula under the long extensor. Its delicate tendon accompanies that of the tibialis anterior to the first metatarsal bone, or becomes lost in the fascia.

4. The =extensor digitalis brevis= has three divisions. It arises on the fibular tarsal bone and the adjacent ligaments. The three tendons are inserted into the second, third, and fourth digits, blending with the interossei. (Sometimes there is found a tendon to the rudimentary first digit, which may represent the extensor hallucis brevis. There may be a fourth belly for the tendon to the second digit.)