Part 33
_Relations._—Anteriorly, the tibia and fibula, the popliteus, lateral extensor, tibialis anterior, and the tibial vessels; posteriorly, the gastrocnemius, superficial flexor, and the tibial nerve; externally, the fascia, skin, and the soleus; internally, the fascia and skin.
_Blood-supply._—Posterior tibial artery.
_Nerve-supply._—Tibial nerve.
5. =Popliteus= (Fig. 203).—This thick and triangular muscle lies on the posterior surface of the femoro-tibial articulation and the posterior surface of the tibia above the popliteal line.
_Origin._—A small depression on the external epicondyle of the femur, close to the articular surface and under the lateral ligament.
_Insertion._—A triangular area on the posterior surface of the tibia, above and internal to the popliteal line; also the proximal half of the inner border and a narrow adjacent part of the internal surface of the tibia.
_Action._—To flex the femoro-tibial joint and to rotate the leg inward.
_Structure._—The strong tendon of origin lies at first under the lateral ligament, and curves backward and inward over the external condyle of the tibia and its semilunar cartilage, being invested by a reflection of the synovial capsule of the joint (Fig. 459). The tendon is succeeded by a thick triangular belly, the fibers of which are directed obliquely downward and inward.
_Relations._—Superficially, the fascia and skin, semitendinosus, gastrocnemius, superficial flexor; deeply, the femoro-tibial joint, the tibia, the popliteal vessels and their divisions. The saphenous vessels and nerve lie along the inner border of the muscle, separated from it, however, by the deep fascia.
_Blood-supply._—Popliteal and posterior tibial arteries.
_Nerve-supply._—Tibial nerve.
MUSCLES OF THE METATARSUS AND DIGIT
=Extensor pedis brevis= (M. extensor digitalis brevis).—This small muscle lies in the angle of union of the long and lateral extensors of the digit. (Shown in Fig. 201, but not marked.)
_Origin._—The outer tendon of the peroneus tertius, the middle annular ligament, and the outer lateral ligament of the hock.
_Insertion._—The tendon of the anterior or long extensor.
_Action._—To assist the anterior or long extensor.
_Structure._—It is principally fleshy, having a superficial origin from the annular ligament, and a deep one (by a thin tendon) from the outer tendon of the peroneus tertius. The insertion is by a thin tendon.
_Relations._—Superficially, the skin and fascia and the tendons of the anterior and lateral extensors; deeply, the joint capsule, the great metatarsal artery, and the deep peroneal nerve.
_Blood-supply._—Great metatarsal artery.
_Nerve-supply._—Deep peroneal nerve.
The =interossei= and =lumbricales= are arranged like those of the thoracic limb, the only noticeable difference being the greater development of the lumbricales in the pelvic limb.
THE MUSCLES OF THE OX
MUSCLES OF THE FACE
The =panniculus= is much more developed than in the horse, presenting as a special feature the extensive =frontalis= muscle, which covers the frontal and nasal regions.
The =orbicularis oris= does not form a complete ring, the defect being in the middle of the upper lip.
The =levator nasolabialis= is extensive, thin, and not very distinct from the frontalis; it divides into two layers, between which the levator labii superioris proprius and the lateral dilator of the nostril pass. The superficial layer ends in the nostril and upper lip, the deep layer on the accessory (lateral) nasal cartilages and on the nasal process of the premaxilla.
The =levator labii superioris proprius= arises on and before the facial tuberosity and terminates by several tendons in the muzzle. It passes between the two layers of the preceding muscle, blending in part with the deep layer.
The =zygomaticus= is much stronger than in the horse. It arises on the masseteric fascia, and ends chiefly in the upper lip.
The =depressor labii superioris= does not resemble the muscle of the same name in the horse. It arises just in front of the facial tuberosity, and divides usually into two branches, which terminate in a number of tendons that form a network in the muzzle and upper lip.
The =incisivus inferior= is a small, rounded muscle, which arises on the body of the mandible below the second and third incisors, and ends in the lower lip, blending with the orbicularis.
The =depressor labii inferioris= is thin, and does not extend as far backward as in the horse; only the anterior end is distinct from the buccinator.
The =buccinator= shows no marked variation, but its superficial layer is well developed.
The =dilatator naris lateralis= arises in front of the facial tuberosity, passes forward between the branches of the levator nasolabialis, and terminates in the outer wing of the nostril.
The dilatator naris transversus is replaced by the =dilatator naris apicalis=, which is situated in the muzzle and joins its fellow at a median raphé. It arises on the border and upper surface of the body of the premaxilla, the fibers passing obliquely upward and outward to the inner wing of the nostril.
The =dilatator naris superior= arises from the alar cartilage of the nostril and ends in the inner wing of the nostril.
[Illustration:
FIG. 207.—MUSCLES OF HEAD OF OX, LATERAL VIEW.
_a_, Levator labii superioris proprius; _b_, levator nasolabialis; _c_, trapezius; _c′_, mastoido-humeralis; _d_, _d′_, sterno-cephalicus; _e_, omo-hyoideus; _f_, dilatator naris lateralis; _g_, zygomaticus; _g′_, malaris; _h_, buccinator; _i_, depressor labii inferioris; _k_, orbicularis oris; _m_, masseter; _n_, parotido-auricularis; _o′_, zygomatico-auricularis and scutulo-auricularis superficialis inferior; _o″_, scutulo-auricularis superficialis superior; _o‴_, scutulo-auricularis superficialis accessorius; _p_, _p′_, scutularis; _u_, frontalis; _w_, mylo-hyoideus; _1_, concha; _2_, _3_, posterior and anterior borders of _1_; _8_, scutiform cartilage; _9_, zygomatic arch; _28′_, ramus of mandible; _37_, external maxillary vein; _38_, jugular vein; _39_, facial vein; _44_, parotid gland; _50_, _50′_, submaxillary gland; dotted line at _50_ indicates position of large lymph gland, and another lies partly under parotid gland, just in front of _44_; _58_, internal palpebral ligament; _59_, laryngeal prominence. (After Ellenberger-Baum, Anat. für Künstler.) ]
The =dilatator naris inferior= consists of two layers which arise on the nasal process of the premaxilla and the lateral nasal cartilage and end in the outer wing of the nostril.
The =orbicularis oculi= is well developed.
The corrugator supercilii is not present as a separate muscle, its place and function being taken by the frontalis.
The =malaris= is broad, and spreads out below on the fascia over the buccinator and masseter; it is divided into two parts.
MUSCLES OF MASTICATION
The =masseter= is not so large as in the horse; a considerable part of it arises on the facial tuberosity and is directed obliquely backward and downward, so that it would draw the lower jaw forward as well as upward.
The =temporalis= conforms to the temporal fossa, and is therefore longer and entirely lateral in position.
The =pterygoidei= are not quite clearly separated; their direction is more oblique, and the origin of the pterygoideus internus is nearer the median plane than in the horse.
[Illustration:
FIG. 208.—MUSCLES OF HEAD OF OX, DORSAL VIEW.
_a_, _a′_, Levator labii superioris proprius; _b_, levator nasolabialis; _f_, dilatator naris lateralis; _g′_, malaris; _o_, zygo-inatico-auricularis and scutulo-auricularis superficialis inferior; _o″_, scutulo-auricularis superficialis superior; _o‴_, scutulo-auricularis superficialis accessorius; _p_, scutularis; _u_, frontalis; _z_, orbicularis oculi; _1_, concave surface of concha; _3_, _2_, anterior and posterior borders of concha; _8_, scutiform cartilage; _34_, parietal cartilage; _39_, facial vein; _49_, muzzle; _58_, internal palpebral ligament. (After Ellenberger-Baum, Anat. für Künstler.) ]
The =stylo-mandibularis= is absent.
The =digastricus= has a tendinous origin on the paramastoid or styloid process of the occipital bone; its bellies are short and thick. It does not perforate the stylo-hyoideus. The two digastrici are connected beneath the root of the tongue by a layer of transverse muscle-fibers (Transversus mandibulæ).
HYOID MUSCLES
The =mylo-hyoideus= is thicker and more extensive than in the horse.
The =stylo-hyoideus= has a long thin tendinous origin and is not perforated by the digastricus.
The =genio-hyoideus= is more developed.
The =kerato-hyoideus= has an additional attachment on the middle cornu of the hyoid bone.
The =hyoideus transversus= is bifid.
The =sterno-thyro-hyoideus= has no intermediate tendon and is thicker.
The =omo-hyoideus= arises as a thin band from the fascia over the third and fourth cervical vertebræ. It blends here with the rectus capitis anterior major. The =occipito-hyoideus= is thick.
[Illustration:
FIG. 209.—MUSCLES OF HEAD OF OX, VENTRAL VIEW.
_d_, _d′_, Sterno-cephalicus; _e_, omo-hyoideus; _g_, zygomaticus; _h_, buccinator; _i_, depressor labii inferioris; _k_, orbicularis oris; _m_, masseter; _n_, parotido-auricularis; _o′_, zygomatico-auricularis; _w_, mylo-hyoideus; _1_, concha, convex surface; _2_, anterior border of concha; _30′_, angle of jaw; _39_, facial vein; _44_, parotid gland; _45_, lower lip; _48_, angle of mouth; _50_, _50′_, submaxillary gland; _59_, larynx; _x_, wing of atlas. (After Ellenberger-Baum, Anat. für Künstler.) ]
MUSCLES OF THE NECK
A. VENTRAL GROUP
The =sterno-cephalicus= consists of two muscles. They arise from the manubrium sterni and first rib. The superficial muscle (Sterno-mandibularis) is inserted on the anterior border of the masseter, the ramus of the mandible, and the buccal fascia. The deep muscle (Sterno-mastoideus) crosses under the preceding and ends on the mastoid process, the mandible, and, in common with the rectus capitis anterior major, on the basilar process of the occipital bone.
[Illustration:
FIG. 210.—SUPERFICIAL MUSCLES OF OX, AFTER REMOVAL OF PANNICULUS.
_a_, Trapezius; _b_, omo-transversarius; _c_, _c′_, mastoido-humeralis (_c_, cleido-mastoideus; _c′_, cleido-occipitalis); _d_, sterno-cephalicus; _e_, deltoid; _f_, long head, _f′_, external head of triceps; _g_, superficial pectoral; _h_, posterior deep pectoral; _i_, serratus magnus; _k_, latissimus dorsi; _l_, obliquus abdominis externus; _l′_, aponeurosis of _l_; _m_, serratus posterior; _m′_, lumbo-dorsal fascia; _n_, obliquus abdominis internus; _o_, tensor fasciæ latæ; _o′_, fascia lata; _p_, gluteus medius; _q_, _q′_, biceps femoris; _r_, semitendinosus; _s_, sacro-coccygeus superior; _t_, sacro-coccygeus lateralis; _u_, coccygeus. (After Ellenberger-Baum, Anat. f Künstler.) ]
There are two scaleni. The =scalenus ventralis= (s. primæ costæ) arises on the first rib and ends on the transverse processes of the third to the seventh cervical vertebræ. It is traversed by the roots of the brachial plexus, which partially divide it into a small dorsal and a large ventral part. The brachial vessels lie below the latter. The =scalenus dorsalis= (s. supracostalis) arises usually on the second, third, and fourth ribs, and ends on the transverse processes of the third to the sixth cervical vertebræ.
The =rectus capitis anterior major= arises on the third to the sixth cervical transverse processes, and blends at its insertion with the sterno-mastoideus and the mastoid portion of the mastoido-humeralis.
The =rectus capitis anterior minor= is larger than in the horse.
The =rectus capitis lateralis= and =longus colli= resemble those of the horse.
The =intertransversales= are large. From the sixth cervical vertebra forward they form a muscular mass (M. intertransversarius longus) which is inserted into the wing of the atlas.
B. LATERAL GROUP
The =splenius= is thin. It arises directly from the first three or four thoracic spines, and ends by a thin tendon on the occipital bone, the wing of the atlas, and the transverse process of the axis, blending with the mastoido-humeralis, trachelo-mastoideus, and omo-transversarius. The remaining muscles present no very marked differential features.
MUSCLES OF THE THORAX
The =levatores costarum= number ten or eleven pairs.
The =diaphragm= presents several important differential features. Its slope is much steeper and its width is greater than in the horse. The costal attachment extends almost in a straight line from the upper fourth of the last rib to the junction of the eighth rib with its cartilage, and along the latter to the sternum. The mid-line slopes from the twelfth thoracic vertebra obliquely as far as the vena cava, beyond which it is almost vertical. The right crus divides into two branches, which circumscribe the œsophageal opening, unite below, and then spread out in the tendinous center. The left crus is small. The œsophageal opening is situated about four to five inches (10 to 12 cm.) below the eighth thoracic vertebra, a little to the left of the median plane. The foramen venæ cavæ is a little more ventral and almost in the median plane. The other muscles resemble those of the horse.
MUSCLES OF THE BACK AND LOINS
The =serratus anticus= is very thin. It is inserted on the fifth to the eighth ribs. It may be reduced to two or three digitations or may be absent. The =serratus posticus= is usually inserted on the last three or four ribs.
The =transversalis costarum= (Iliocostalis) has a distinct lumbar portion which is attached to the lumbar transverse processes and the external angle of the ilium.
The =longissimus= resembles that of the horse, but it is more fleshy anteriorly, and the spinalis dorsi is clearly distinguishable from the common mass. In the lumbar region the tendons meet across the summits of the spines.
=Intertransversales= are present in the back, and =interspinales= in the back and loins.
MUSCLES OF THE TAIL
These resemble those of the horse; the coccygeus is, however, much more developed.
ABDOMINAL MUSCLES
The =obliquus abdominis externus= is somewhat thinner and has a less extensive origin, which begins at the lower part of the fifth intercostal space and ends on the last rib above its middle. The direction of the fibers in the flank is horizontal, and they do not reach to the external angle of the ilium, nor as high as the lumbar transverse processes. (In this region the abdominal tunic has a strong attachment to the point of the hip and the lumbo-dorsal fascia.) The aponeurosis is intimately united with the abdominal tunic, and does not detach a layer on the inner surface of the thigh.
[Illustration:
FIG. 211.—DEEPER MUSCLES OF NECK, SHOULDER, AND THORAX OF OX.
_c′_, Cleido-occipitalis muscle; _d_, sterno-cephalicus; _f_, _f′_, long and external heads of triceps; _g_, superficial pectoral muscle; _h_, _h′_, posterior and anterior deep pectoral muscles; _i_, _i′_, serratus magnus; _k_, latissimus dorsi; _l_, obliquus abdominis externus; _v′_, biceps brachii; _w_, splenius; _x_, rhomboideus; _y_, trachelo-mastoideus; _z_, supraspinatus; _z′_, infraspinatus; _z″_, tendon of insertion of _z′_; _1′_, cartilage of scapula; _2_, tuberosity of spine of scapula; _3_, acromion; _5_, external tuberosity of humerus; _6_, deltoid tuberosity; _8_, olecranon; _26_, transverse processes of cervical vertebræ; _27_, posterior auricular muscles; _X_, wing of atlas. (After Ellenberger-Baum, Anat. für Künstler.) ]
The =obliquus abdominis internus= is more developed and has an additional origin from the lumbo-dorsal fascia. The aponeurosis blends with that of the external oblique near the linea alba, and detaches a layer which assists in the formation of the internal sheath of the rectus.
The =rectus abdominis= arises on the lateral border of the sternum as far forward as the third costal cartilage. The two muscles are separated, except near the pelvis, by an interval varying from two to four inches (ca. 5 to 10 cm.), so that this part of the abdominal wall is entirely fibrous. (The umbilicus is in a transverse plane through the third lumbar vertebra.) There are five tendinous inscriptions, on the third of which is a foramen for the passage of the subcutaneous abdominal vein (milk vein). The prepubic tendon has, in addition to branches inserted into the ilio-pectineal eminences, a strong attachment to the median common tendon of the adductors of the thigh, so that the abdominal wall is strongly retracted and almost vertical at its junction with the pelvis.
The =transversus abdominis= presents no striking differential features. The transversalis fascia is strong and distinct except over the diaphragm.
MUSCLES OF THE THORACIC LIMB
I. MUSCLES OF THE SHOULDER GIRDLE
The =trapezius= is much thicker and broader than in the horse, and is undivided. It arises on the ligamentum nuchæ and supraspinous ligament, from the atlas to the twelfth thoracic vertebra.
The =omo-transversarius= is a muscle (not present in the horse) which arises on the wing of the atlas, and, inconstantly, the transverse process of the second cervical vertebra, and is inserted into the scapular spine and fascia.
The =rhomboideus= is clearly divided into cervical and dorsal portions, the latter extending further than in the horse.
The =latissimus dorsi= has a broad tendon of origin, which blends with the lumbo-dorsal fascia; it is also attached to the eleventh and twelfth ribs, the fascia over the external intercostal and oblique abdominal muscles, and by a tendinous slip to the deep pectoral muscle.
The =mastoido-humeralis= has two distinct parts. The dorsal division (M. cleido-occipitalis) arises on the occipital bone and the ligamentum nuchæ. The ventral part (M. cleido-mastoideus) is smaller and arises by a round tendon on the mastoid process and the rectus capitis anterior major, and by a thin tendon on the mandible. At the shoulder a small muscle which arises on the first rib blends with the deep face of the mastoido-humeralis.[75]
The =superficial pectoral= muscle does not present any striking difference.
The =deep pectoral= arises as far forward as the second rib and is undivided. However, the scapular portion may be considered to be represented by a small branch extending over the lower part of the supraspinatus. A tendon is detached from the dorsal edge, which blends with the latissimus dorsi and coraco-brachialis.
The =serratus magnus= is clearly divided into cervical and thoracic portions. The former is large and extends from the third (or second) cervical vertebra to the fifth rib, being overlapped behind by the thoracic part. The thoracic part is relatively thin and is covered by a very strong aponeurosis; it is attached to the fourth to the ninth ribs by six digitations, and is inserted by a flat tendon into the inner face of the dorsal angle of the scapula.
II. MUSCLES OF THE SHOULDER
The =deltoid= is clearly divided into acromial and scapular portions. The former arises on the acromion, the latter on the posterior border of the scapula and the aponeurotic covering of the infraspinatus. The scapular part of the muscle is largely inserted into the fascia covering the triceps.
The =supraspinatus=, =infraspinatus=, and =teres minor= do not differ materially from those of the horse.
The =subscapularis= consists of three portions with a common tendon of insertion.
The =teres major= and =coraco-brachialis= resemble those of the horse.
III. MUSCLES OF THE ARM
The =biceps= is smaller and less tendinous, and is situated more internally than in the horse. The tendon of origin is flat, and is bound down in the bicipital groove by a fibrous band. (In the sheep the tendon is round and passes through the shoulder joint.)
[Illustration:
FIG. 212.—MUSCLES OF ANTIBRACHIUM AND MANUS OF OX, ANTERIOR VIEW.
_a_, Extensor carpi radialis; _b_, extensor digiti tertii; _c_, extensor digitalis communis; _d_, extensor digiti quarti (tendon); _f_, extensor carpi obliquus; _g_, brachialis; _12′_, metacarpal tuberosity. (After Ellenberger-Baum, Anat. für Künstler.) ]
[Illustration:
FIG. 213.—MUSCLES OF ANTIBRACHIUM AND MANUS OF OX, EXTERNAL VIEW.
_a_, Extensor carpi radialis; _b_, extensor digiti tertii; _c_, common or anterior digital extensor; _d_, extensor digiti quarti; _e_, flexor carpi externus; _f_, extensor carpi obliquus; _f′_, ulnar head of flexor carpi medius; _g_, brachialis; _h_, interosseus medius or suspensory ligament; _i_, flexor tendons; _i′_, branch of _h_, to superficial flexor tendon; _8_, olecranon; _11_, accessory carpal bone; _12′_, metacarpal tuberosity. (After Ellenberger-Baum, Anat. für Künstler.) ]
[Illustration:
FIG. 214.—MUSCLES OF ANTIBRACHIUM AND MANUS OF OX, INTERNAL VIEW.
_a_, Extensor carpi radialis; _b_, tendon of extensor digiti tertii; _f_, tendon of extensor carpi obliquus; _g_, brachialis; _h_, interosseus medius or suspensory ligament; _i_, flexor tendons; _i′_, branch of _h_; _k_, flexor carpi internus; _l_, flexor carpi medius; _m_, superficial digital flexor. (After Ellenberger-Baum, Anat. für Künstler.) ]
The internal head of the =triceps= is more developed than in the horse.
The =tensor fasciæ antibrachii= is a slender muscle.
IV. MUSCLES OF THE FOREARM
A. EXTENSOR DIVISION
The =extensor carpi radialis= is like that of the horse. There is sometimes a small muscle lying along its inner border, which may represent the extensores pollicis.
There are three =digital extensors=: 1. The =common= or =anterior digital extensor= (M. extensor digitalis communis) arises by two heads from the extensor epicondyle and the ulna. The heads fuse about the middle of the forearm, and terminate soon on a tendon which passes over the carpus and metacarpus, gradually inclining forward. At the fetlock joint it divides into two branches, which are inserted into the third phalanges. 2. The =internal digital extensor= (M. extensor digiti tertii proprius) arises on the extensor epicondyle, and is inserted by two branches into the second and third phalanges of the inner digit. The tendon receives two reinforcing slips from the suspensory ligament. 3. The =lateral digital extensor= (M. extensor digitalis lateralis s. digiti quarti proprius) arises from the external lateral ligament of the elbow joint, the external tuberosity of the radius, and the ulna. The tendon terminates like that of the preceding muscle.
[Illustration:
FIG. 215.—RIGHT CARPUS OF OX WITH BURSÆ AND SYNOVIAL SHEATHS INJECTED, EXTERNAL VIEW. ]
[Illustration:
FIG. 216.—RIGHT CARPUS OF OX WITH BURSÆ AND SYNOVIAL SHEATHS INJECTED, INTERNAL VIEW.
_1_, Extensor carpi radialis, with synovial sheath (_1′_) and bursa (_1″_); _2_, extensor carpi obliquus, with synovial sheath (_2′_) and bursa (_2″_); _3_, extensor digiti tertii proprius; _4_, extensor digitalis communis; _3′_, common synovial sheath of _3_ and _4_; _5_, extensor digiti quarti proprius, with synovial sheath (_5′_); _6_, _6′_, flexor carpi externus, with bursa (_6″_); _7_, flexor carpi internus, with synovial sheath; _8_, deep digital flexor, with synovial sheath (_8′_); _9_, flexor carpi medius; _10_, superficial digital flexor, with synovial sheath _10′_; _a_, radius; _b_, carpus; _c_, metacarpus; _d_, cut edge of annular ligament. (After Schmidtchen.) ]
The =extensor carpi obliquus= resembles that of the horse.
The extensor tendons are bound down at the carpus by an annular ligament, and are furnished with synovial sheaths (Figs. 215, 216).
B. FLEXOR DIVISION
The three =flexors of the carpus= are like those of the horse.
The =superficial digital flexor= is somewhat blended at its origin with the middle flexor of the carpus. It divides into two bellies, superficial and deep, terminating on tendons at the distal part of the forearm. The superficial tendon passes over the posterior annular ligament (Ligamentum carpi transversum), perforates the metacarpal fascia, and joins the deep tendon about the middle of the metacarpus. The deep belly is connected with the deep flexor by a strong fibrous band. Its tendon passes under the annular ligament in a groove on the deep flexor, from which it receives fibers. The conjoined tendon soon bifurcates, each branch receiving a reinforcing band from the suspensory ligament, and forming near the fetlock a ring for the corresponding branch of the deep flexor tendon. Passing under two digital annular ligaments, they are inserted into the volar surfaces of the second phalanges by three slips.
The =deep digital flexor= has the same heads as in the horse, the humeral head, as before mentioned, being connected with the deep portion of the superficial flexor. The tendon divides near the distal end of the metacarpus into two branches which are inserted into the volar surfaces of the third phalanges.
The synovial sheaths at the carpus present the following special features: One is found in connection with the tendon of the superficial part of the superficial flexor of the digits. There is a common sheath for the tendons of the common extensor and the inner extensor.
Bursæ may occur under the tendons of the proper extensors of the digits at the fetlock; they are constant only in old animals (Schmidtchen). The branches of the tendon of the common extensor are provided with synovial sheaths from their origin to the middle of the second phalanx. There are two digital synovial sheaths for the flexor tendons; they may communicate at their upper part, and extend from the distal third of the metacarpus nearly to the distal sesamoids. Bursæ occur between the latter and the branches of the deep flexor tendon.
METACARPAL MUSCLES
The =lumbricales= are absent, unless we regard as such the muscular bundles which arise on the deep flexor and are inserted into the superficial flexor tendon at the carpus.