Part 34

The =interosseus medius= or suspensory ligament is somewhat more muscular than in the horse; indeed, in the young subject it may be almost entirely fleshy. Its arrangement is somewhat complex. Single at its origin, it detaches about the middle of the metacarpus a band which joins the tendon of the superficial flexor and concurs near the fetlock in the formation of the ring for the deep flexor tendon. A little lower down it divides into three and then into five branches. The lateral branches (two pairs) are attached to the corresponding sesamoids and tendons of the proper extensors, while the middle branch passes through the sulcus at the distal end of the metacarpus and bifurcates, each division fusing with the tendon of the corresponding proper extensor.

[Illustration:

FIG. 217.—CROSS-SECTION OF DISTAL THIRD OF METACARPUS OF OX.

_b_, Tendon of extensor digiti tertii; _c_, tendon of common extensor; _d_, tendon of extensor digiti quarti; _h_, interosseus medius or suspensory ligament; _i_, tendons of digital flexors; _i′_, branch of _h_; _12_, metacarpal bone. (After Ellenberger-Baum, Anat. für Künstler.) ]

It is to be noted that the fascia on the posterior face of the metacarpus and digit is very thick. It is continuous above with the ligamentum carpi transversum, and is attached on either side to the metacarpal bone. At the fetlock it forms the fibrous basis for the small claws, and below this it detaches two strong bands which diverge to be inserted into the second and third phalanges, blending with the lateral ligaments.

THE MUSCLES OF THE PELVIC LIMB

I. THE SUBLUMBAR MUSCLES

The =psoas minor= begins at the disc between the twelfth and thirteenth thoracic vertebræ.

The =psoas major= has a fleshy origin on the posterior border of the last rib, and a thin tendon attached to the twelfth rib.

The =iliacus= begins under the body of the sixth lumbar vertebra, and is more closely united with the psoas major than in the horse.

The =quadratus lumborum= extends as far forward as the body of the tenth or eleventh thoracic vertebra.

II. EXTERNAL MUSCLES OF THE HIP AND THIGH

The =tensor fasciæ latæ= is large, and the fleshy part extends further down than in the horse.

The gluteus superficialis is not present as such; apparently its anterior part has fused with the tensor fasciæ latæ and its posterior with the biceps femoris.

The =gluteus medius= is small, the lumbar portion being insignificant and extending forward only to the fourth lumbar vertebra. Its deep portion (Gluteus accessorius) is easily separable, and its strong tendon is inserted into the femur below the trochanter major, under cover of the upper part of the vastus externus.

The =gluteus profundus= is thin, but extensive, arising as far forward as the external angle of the ilium, and from the lower part of the sacro-sciatic ligament. The fibers converge on a tendon which passes under the upper part of the vastus externus, and is inserted into a tubercle a short distance below the great trochanter.

[Illustration:

FIG. 218.—GLUTEAL AND FEMORAL REGIONS OF OX, AFTER REMOVAL OF SUPERFICIAL MUSCLES.

_p_, Gluteus medius; _r_, semitendinosus; _u_, coccygeus; _28_, vastus externus; _28′_, rectus femoris; _29_, semimembranosus; _30_, gastrocnemius; _31_, sacro-sciatic ligament; _16_, tuber coxæ; _17_, tuber ischii; _19_, trochanter major; _20_, patella; _21′_, external condyle of tibia. (After Ellenberger-Baum. Anat. für Künstler.) ]

The =biceps femoris= is very wide at its upper part, having apparently absorbed the posterior part of the superficial gluteus. It is divided in the thigh into two portions, which end on a wide aponeurosis. There is no femoral attachment. A large bursa occurs between the muscle and the great trochanter in the adult. The part of the tendon which fuses with the external patellar ligament presents a fibro-cartilaginous thickening, and an extensive bursa is interposed between it and the external condyle of the femur.

The =semitendinosus= and =semimembranosus= arise on the ischium only. The latter has a branch attached to the internal condyle of the tibia.

III. ANTERIOR MUSCLES OF THE THIGH

The =quadriceps femoris= resembles that of the horse; the =vastus intermedius= is more clearly separable, and consists of two parts. Bursæ occur under the insertions of the internal and external vasti, and often under the end of the biceps in the adult.

[Illustration:

FIG. 219.—MUSCLES OF LEFT LEG AND FOOT OF OX, ANTERIOR VIEW.

_a_, Peroneus tertius; _a′_, tibialis anterior; _b_, anterior or long digital extensor; _b′_, extensor digiti tertii; _c_, peroneus longus; _d_, extensor digiti quarti; _i_, _i_, annular ligaments; _k_, external lateral ligament of hock joint; _l_, branch of suspensory ligament; _20_, patella; _21′_, external condyle of tibia; _28_, tuberosity of tibia. (After Ellenberger-Baum, Anat. für Künstler.) ]

[Illustration:

FIG. 220.—MUSCLES OF LEG AND FOOT OF OX, EXTERNAL VIEW.

_a_, Peroneus tertius; _a′_, tibialis anterior; _b_, anterior or long digital extensor; _b′_, tendon of _b_; _c_, peroneus longus; _d_, extensor digiti quarti; _e_, deep digital flexor; _e′_, tendon of _e_; _e″_, branch of interosseus medius or suspensory ligament; _f_, gastrocnemius (the soleus lies just in front of _f_); _f′_, tendon of _f_; _g_, tendon of superficial digital flexor; _h_, interosseus medius or suspensory ligament; _i_, _i_, annular ligaments; _20_, patella; _21′_, external condyle of tibia; _28_, crest of tibia. (After Ellenberger-Baum, Anat. für Künstler.) ]

The =articularis genu= or subcrureus is a small muscle which lies under the lower part of the vastus intermedius, and is inserted on the suprapatellar cul-de-sac of the synovial membrane.

The =capsularis= is absent.

IV. INTERNAL MUSCLES OF THE THIGH

The =sartorius= arises by two heads, one from the tendon of the psoas minor and the iliac fascia, the other from the shaft of the ilium. The femoral vessels pass between them.

The =gracilis= is more extensively united with its fellow than in the horse.

[Illustration:

FIG. 221.—LEFT TARSUS OF OX WITH SYNOVIAL SHEATHS AND BURSÆ INJECTED, EXTERNAL VIEW.

_1_, Peroneus tertius; _1′_, tendon of _1_ and its sheath, _1″_; _2_, extensor digiti tertii proprius; _2′_, tendon of _2_; _2″_, common sheath of tendons of extensor digiti tertii and extensor digitalis longus (_3_, _3′_); _4_, peroneus longus and its sheath, _4′_; _5_, extensor digiti quarti and its sheath, _5′_; _6_, tendon of gastrocnemius; _7_, superficial digital flexor and its sheath, _7′_; _8_, tendon of tibialis anterior; _a_, tibia; _b_, proximal annular ligament; _c_, tarsus; _d_, distal annular ligament; _e_, metatarsus; _f_, external lateral ligament. (After Schmidtchen.) ]

[Illustration:

FIG. 222.—LEFT TARSUS OF OX WITH SYNOVIAL SHEATHS AND BURSÆ INJECTED, INTERNAL VIEW.

_1_, Peroneus tertius; _2_, tendon of tibialis anterior with sheath, _2′_, and bursa, _2″_; _3_, long digital flexor and _3′_, its sheath; _4_, tibialis posterior; _5_, deep digital flexor and its sheath, _5′_; _6_, tendon of gastrocnemius and bursa, _6′_; _7_, superficial digital flexor and its sheath, _7′_; _8_, subcutaneous bursa; _a_, tibia; _b_, proximal annular ligament; _c_, tarsus; _d_, metatarsus. (After Schmidtchen.) ]

The =pectineus= is large, and arises by a single head from the pubic crest and prepubic tendon. It divides into two branches, one of which is inserted as in the horse, while the other extends to the internal epicondyle of the femur.

The =adductor= resembles that of the horse, but does not reach to the internal condyle.

The =quadratus femoris= and =obturator externus= resemble those of the horse.

The =obturator internus= arises from the ischium only, and its tendon passes through the obturator foramen.

The =gemellus= is large.

V. MUSCLES OF THE LEG AND FOOT

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.

[Illustration:

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.

[Illustration:

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.) ]

[Illustration:

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.

[Illustration:

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=.

[Illustration:

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