Fig. 200.—Cross-section of Middle of Right Thigh of Horse.
Origin.—The external border and surface of the femur, from the great trochanter to the supracondyloid fossa.
Insertion.—(1) The outer part of the anterior surface of the patella; (2) the tendon of the rectus femoris.
Action.—To extend the stifle joint.
Structure.—The fibers are directed downward and forward, many being inserted into the tendinous sheet which covers the side of the rectus. A bursa is often found between the distal end and the patella.
Relations.—Externally, the fascia lata and skin, tensor fasciæ latæ, superficial gluteus, and biceps femoris; internally, the femur and femoro-patellar joint capsule, the rectus femoris, vastus intermedius, and the iliaco-femoral artery.
Blood-supply.—Iliaco-femoral artery.
Nerve-supply.—Femoral nerve.
(3) Vastus internus (s. medialis).—This is smaller than the preceding muscle, and lies in a similar position on the inner side of the thigh.
Origin.—The internal surface of the femur, from the neck to the distal third.
Insertion.—(1) The upper part of the inner border of the patella and its cartilage; (2) the tendon of the rectus femoris.
Action.—To extend the stifle joint.
Structure.—This is very similar to that of the vastus externus. It is, however, more difficult to separate from the intermedius, because many fibers of the latter arise on the tendinous sheet which covers the contact surface of the inner vastus. Its insertion into the patella is chiefly by means of a broad strong tendon. From the deep face fleshy fibers are inserted also into the femoro-patellar capsule.
Relations.—Internally, the skin and fascia lata, the iliacus, sartorius, pectineus, and adductor, the femoral vessels and saphenous nerve; externally, the femur, femoro-patellar joint capsule, rectus femoris, and vastus intermedius, the anterior femoral artery, and branches of the femoral nerve.
Blood-supply.—Femoral and anterior femoral arteries.
Nerve-supply.—Femoral nerve.
(4) Vastus intermedius (Crureus).—This muscle is deeply situated on the anterior face of the femur, and is entirely covered by the preceding heads.
Origin.—(1) The anterior and external surfaces of the femur, from the proximal to the distal fourth; (2) the aponeurosis of the vastus internus.
Insertion.—(1) The base of the patella; (2) the femoro-patellar joint capsule.
Action.—(1) To extend the stifle joint; (2) to tense (raise) the femoro-patellar capsule during extension of the joint.
Structure.—The muscle is usually quite difficult to isolate from the other vasti, so that many since Günther have declared it an artefact.[71] It is entirely fleshy, and is small at its proximal end, but when traced downward increases in bulk by the accession of fibers arising on the femur and the tendinous covering of the vastus internus. The terminal part is intimately adherent to the femoro-patellar joint capsule, where the latter bulges upward above the level of the patella.
Relations.—Internally, the vastus internus; externally, the vastus externus; anteriorly, the rectus; posteriorly, the femur and femoro-patellar capsule.
Blood-supply.—Iliaco-femoral and anterior femoral arteries.
Nerve-supply.—Femoral nerve.
The straight ligaments of the patella are to be regarded as tendons of the quadriceps which communicate the action of the latter to the tibia, the patella being intercalated as a sesamoid bone.
3. Capsularis (Fig. 154) (Rectus parvus).—This is a small muscle (scarcely as large as one’s finger), which arises on the ilium immediately above the outer tendon of the rectus femoris, and passes down between the vastus internus and externus to be inserted into the anterior surface of the femur. It passes over the front of the hip joint, to the capsule of which some fibers are attached. Sometimes the muscle has two distinct heads, in which case the additional head arises between the two tendons of origin of the rectus femoris. Its action may be to raise the capsule during flexion of the joint.
IV. THE MUSCLES OF THE LEG AND FOOT
Fig. 201.—Muscles of Lower Part of Thigh, Leg, and Foot of Horse, External View.
o′, Fascia lata; q, q′, q″, biceps femoris; r, semitendinosus; 21′, external condyle of tibia. (After Ellenberger-Baum, Anat. für Künstler.)
The muscles of this region cover almost all of the tibia except its internal face, which is largely subcutaneous. As in the forearm, the muscles fall into two groups, an anterior or dorso-lateral, and a posterior or plantar. The muscles of the first group are extensors of the digit and flexors of the hock, those of the second have the opposite action.
A. Anterior Group
1. Anterior or long digital extensor (M. extensor digitalis longus; extensor pedis; anterior extensor of the phalanges).—This muscle is situated superficially on the antero-external aspect of the leg, and is provided with a long tendon which passes down over the front of the tarsus, metatarsus, and digit.
Origin.—The small fossa (Fossa extensoria) between the external condyle and the trochlea of the femur.
Insertion.—(1) The extensor process of the third phalanx; (2) the anterior surface of the proximal extremities of the first and second phalanges.
Action.—To extend the digit and flex the hock. It also assists in fixing the stifle joint.
Structure.—The origin is by means of a strong tendon in common with the peroneus tertius, on which also many fibers arise. The common tendon passes downward in the groove between the outer condyle and the tuberosity of the tibia, where a pouch from the femoro-tibial capsule descends four or five inches (ca. 10 to 12 cm.) beneath the tendon. The belly is fusiform and somewhat flattened. The long tendon of insertion begins in the belly about its middle, and is clear of the fleshy part near the tarsus. It passes downward over the front of the hock, bound down by the three annular ligaments already described (see crural fascia), and enveloped by a synovial sheath which begins a little above the level of the external malleolus, and extends nearly to the junction with the lateral extensor tendon. This union occurs usually about a hand’s breadth below the tarsus. In the angle of union the extensor brevis also joins the principal tendon. Beyond this point the arrangement is the same as in the fore limb.
Relations.—Superficially, the skin and fascia; deeply, the femoro-tibial capsule, peroneus tertius, and tibialis anterior; behind, the lateral extensor and the superficial and deep peroneal nerves. In front of the tarsus the anterior tibial artery crosses the deep face of the tendon (Fig. 460).
Blood-supply.—Anterior tibial artery.
Nerve-supply.—Peroneal nerve.
2. Lateral digital extensor (M. extensor digitalis lateralis; peroneus; lateral extensor of the phalanges).—This muscle lies on the outer surface of the leg, behind the preceding one.
Origin.—The external lateral ligament of the stifle joint, the fibula, the external border of the tibia, and the interosseus ligament.
Insertion.—The tendon of the anterior extensor, about a third of the way down the metatarsus.
Action.—To assist the anterior extensor.
Structure.—The belly is fusiform, flattened, and pennate. The tendon runs through the entire length of the belly and becomes free from it at the lower fourth of the tibia. It passes downward through the groove on the external malleolus, bound down by an annular ligament, and, inclining forward, blends (usually) with the tendon of the anterior extensor. It is provided with a synovial sheath, which begins about one inch (ca. 2 to 3 cm.) above the external malleolus and ends about one and one-half inches (ca. 3 to 4 cm.) above the junction. Sometimes the fusion does not occur, and the tendon then passes down the metatarsus, alongside of that of the long extensor, to lie inserted into the first phalanx like the corresponding muscle of the thoracic limb.
Relations.—Externally, the skin and fascia and the superficial peroneal nerve; internally, the tibia and fibula; anteriorly, the intermuscular septum, the long extensor, and the tibialis anterior; posteriorly, the deep flexor and the soleus.
Blood-supply.—Anterior tibial artery.
Nerve-supply.—Peroneal nerve.
3. Peroneus tertius (Tendinous part of the flexor metatarsi; tendo femorotarseus [Schmaltz]).—This consists in the horse of a strong tendon which lies between the anterior extensor and the tibialis anterior.[72]
Fig. 202.—Muscles of Pelvic Limb of Horse, Anterior View. y, Rectus femoris; 20, patella. (After Ellenberger-Baum, Anat. für Künstler.)
Origin.—The fossa extensoria (between the external condyle and the trochlea of the femur), in common with the anterior extensor.
Insertion.—(1) The proximal extremities of the large (third) and external small (fourth) metatarsal bones, and the third tarsal bone; (2) the fibular and fourth tarsal bones.
Action.—Mechanically to flex the hock when the stifle joint is flexed.
Structure.—This is entirely tendinous. The proximal end and the underlying prolongation of the synovial membrane of the femoro-tibial joint have been mentioned in the description of the anterior extensor. Fibers of the latter muscle and of the tibialis anterior arise on the tendon as it passes downward to the front of the hock. At the distal end of the tibia the tendon divides into two branches, between which the tendon of the tibialis anterior emerges. The anterior branch is attached to the third tarsal and third and fourth metatarsal bones, while the outer one curves outward, bifurcates, and is inserted into the fibular and fourth tarsal bones (Fig. 460).
Relations.—Superficially, the anterior extensor; deeply, the tibialis anterior. The anterior tibial vessels cross the deep face of the outer branch.
4. Tibialis anterior (Muscular portion of the flexor metatarsi).—This lies on the antero-external face of the tibia; it is wide and flattened above, pointed below.
Origin.—The external condyle and border of the tibia and a small area on the external surface of the tuberosity.
Insertion.—(1) The metatarsal tuberosity; (2) the first and second tarsal bones.
Action.—To flex the hock joint.
Structure.—The origin is fleshy, and is divided by the groove in which lie the common tendon of the long extensor and peroneus tertius and a synovial pouch. Passing downward on the tibia, the belly is united by tendinous and fleshy fibers with the peroneus tertius, and terminates close to the tarsus in a point on the tendon of insertion. The latter emerges between the branches of the peroneus tertius and bifurcates, the anterior branch being inserted into the metatarsal tuberosity, the inner one (cunean tendon) into the fused first and second tarsal bones (cuneiform parvum). The tendon is provided with a synovial sheath at its emergence, and a bursa (cunean bursa) is interposed between the inner branch and the internal lateral ligament.
Relations.—Superficially, the anterior and lateral extensors, the peroneus tertius, and the deep peroneal nerve; deeply, the tibia, the deep flexor, and the anterior tibial vessels.
Blood-supply.—Anterior tibial artery.
Nerve-supply.—Peroneal nerve.
B. Posterior Group
1. Gastrocnemius (Figs. 179, 201, 203).—This muscle extends from the lower third of the femur to the point of the hock. It arises by two heads.
Origin.—(1) Outer head, from the external rough margin of the supracondyloid fossa (Fossa plantaris); (2) inner head, from the supracondyloid crest.
Insertion.—The posterior part of the tuber calcis.
Action.—To extend the hock.
Structure.—The two bellies are thick, fusiform, and somewhat flattened. They are covered by a strong aponeurosis and contain tendinous intersections. They terminate toward the middle of the leg on a common tendon (Tendo calcaneus s. Achillis), which at first lies posterior to that of the superficial flexor, but, by a twist in both, comes to lie in front of the latter. The deep fascia blends with the tendon throughout its length, and the soleus muscle is inserted into its anterior edge. A small bursa (Bursa tendinis calcanei) lies in front of the insertion on the tuber calcis, and a large bursa is interposed between the two tendons from the twist downward. The superficial flexor lies between the two heads and is adherent to the outer one (Fig. 459).
Relations.—Anteriorly, the stifle joint, the superficial flexor, popliteus, deep flexor, popliteal vessels, and tibial nerve; internally (above), the semitendinosus, semimembranosus, and adductor, (below) the fascia and skin; externally (above), the biceps femoris and peroneal (anterior tibial) nerve, (below) the fascia and skin.
Fig. 203.—Muscles of Leg and Foot of Horse, Internal View.
r′, Tendon of semitendinosus; w, gracilis; x, sartorius; y, vastus internus. (After Ellenberger-Baum, Anat. für Künstler.)
Blood-supply.—Popliteal artery.
Nerve-supply.—Tibial nerve.
2. Soleus (Fig. 201).—This muscle is very small in the horse. It lies immediately under the deep fascia, on the proximal half of the outer surface of the leg, and is directed obliquely downward and backward.
Origin.—The head of the fibula.
Insertion.—The tendon of the gastrocnemius, about the middle of the leg.
Action.—To assist the gastrocnemius.
Structure.—It is a thin, fleshy band, about an inch (ca. 2 to 3 cm.) in width, terminating on a thin tendon which fuses with that of the gastrocnemius.[73]
Relations.—Superficially, the skin, fascia, and peroneal nerve; deeply, the lateral extensor and deep flexor.
Blood-supply.—Posterior tibial artery.
Nerve-supply.—Tibial nerve.
3. Superficial digital flexor or flexor pedis perforatus (Figs. 199, 201, 203) (M. flexor digitalis pedis sublimis; superficial flexor of the phalanges).—The proximal part of this muscle lies between and under cover of the two heads of the gastrocnemius (Fig. 459). It consists almost entirely of a strong tendon, the belly being very little developed.
Fig. 204.—Cross-section of Left Leg of Horse; Section is Cut a Little Above Middle of Region.
a, Tibia; b, fibula; c, tibialis anterior; d, peroneus tertius; e, anterior or long digital extensor; f, lateral extensor; g, deep head of deep flexor (flexor hallucis longus); h, inner head of deep flexor (flexor accessorius s, digitorum longus); i, superficial head of deep flexor (tibialis posterior); k, popliteus; l, superficial flexor tendon; m, gastrocnemius tendon; n, soleus; o, skin; p, anterior tibial artery; q, superficial peroneal nerve; q′, deep peroneal nerve; r, branch of q; s, posterior tibial artery; t, cutaneous nerve; u, tibial nerve; v, recurrent tibial vein; w, saphenous artery; x, saphenous vein; y, branches of saphenous nerve. (After Ellenberger, inl Leisering’s Atlas.)
Origin.—The supracondyloid fossa (Fossa plantaris) of the femur.
Insertion.—(1) The front and sides of the tuber calcis; (2) the eminences on the proximal extremity of the second phalanx, and the distal extremity of the first phalanx behind the lateral ligament.
Action.—To flex the digit and extend the hock joint. On account of the exceedingly small amount of muscular tissue the action is to be regarded chiefly as a mechanical effect, resulting from the action of other muscles on the stifle joint.
Structure.—The origin is by means of a strong round tendon which is incompletely covered with fleshy fibers as far as the upper third of the leg. It is pretty intimately attached to the gastrocnemius, especially to the outer head. At the distal third of the tibia it winds around the inner surface of the gastrocnemius tendon, and then occupies a position behind the latter. At the point of the hock it widens out, forming a sort of cap over the tuber calcis, detaching on either side a strong band which is inserted into the tuber calcis with the tarsal tendon of the biceps and semitendinosus. It then passes downward over the plantar (Calcaneo-metatarsal) ligament, becomes narrower, and is arranged below as in the thoracic limb. A large synovial bursa lies under the tendon from the distal fourth of the tibia to the middle of the tarsus. A subcutaneous bursa is sometimes found on the wide part of the tendon at the point of the hook. (Either or both of these bursæ may be involved in so-called “capped hock.”)
Relations.—Posteriorly, the gastrocnemius, fascia, and skin; anteriorly, the femoro-patellar capsule, the popliteus, the deep flexor, and the popliteal vessels; internally, the tibial nerve.
Blood-supply.—Femoro-popliteal artery.
Nerve-supply.—Tibial nerve.
Fig. 205.—Injected Synovial Sheaths and Bursæ of Tarsal Region of Horse, Inner View.
a, Synovial sheath of peroneus tertius and tibialis anterior; b, bursa under inner (cunean) tendon of tibialis anterior; c, synovial sheath of flexor longus s. accessorius; d, tarsal sheath of deep flexor; e, e′, bursa under superficial flexor tendon; f, f′, tibio-tarsal joint capsule; 1, anterior extensor; 2, tibialis anterior; 2′, inner (cunean) tendon of 2; 3, flexor longus; 4, deep digital flexor; 5, superficial flexor tendon; 6, gastrocnemius tendon; 7, tibia; 8, tarsus; 9, tuber calcis; 10, large metatarsal bone; 11, inner small metatarsal bone; 12, 12′, fascial bands. (After Ellenberger, in Leisering’s Atlas.)
Fig. 206.—Injected Synovial Sheaths and Bursæ of Tarsal Region of Horse, External View.
a, Synovial sheath of anterior or long digital extensor; b, synovial sheath of lateral digital extensor; c, c′, bursa under superficial flexor tendon; d, capsule of hock joint; 1, anterior or long extensor; 2, lateral extensor; 3, 3, 3, annular ligaments; 4, deep digital flexor; 5, tendon of gastrocnemius; 6, superficial flexor tendon; 7, tibia; 8, tarsus; 9, tuber calcis; 10, metatarsus. (After Ellenberger, in Leisering’s Atlas.)
4. Deep digital flexor or flexor pedis perforans (M. flexor digitalis pedis profundus; deep and oblique flexors of the phalanges).—The belly of this muscle lies on the posterior surface of the tibia, and is divisible into three parts or heads, which, however, finally unite on a common tendon of insertion.
Origin.—(1) The posterior edge of the external condyle of the tibia; (2) the external border of the external condyle of the tibia, just behind the facet for the fibula; (3) the middle third of the posterior surface and the upper part of the external border of the tibia, the posterior border of the fibula, and the interosseous ligament.[74]
Insertion.—The semilunar crest of the third phalanx and the adjacent surface of the lateral cartilage.
Action.—To flex the digit and to extend the hock joint.
Structure.—(1) The inner head (M. flexor digitalis longus s. flexor accessorius) is easily isolated (Figs. 203, 459). It has a fusiform belly, which crosses the leg obliquely and lies in a groove formed by the other heads and the popliteus. This terminates near the lower third of the tibia on a round tendon which passes downward, partly embedded in the internal lateral ligament of the hock, and joins the common tendon about a third of the way down the metatarsus. In its course over the inner surface of the hock the tendon lies in a canal formed by the strong tarsal fascia, the tibia, and the lateral ligament, and is provided with a synovial sheath which extends from the distal fourth of the tibia to the junction with the principal tendon. (2) The superficial head (M. tibialis posterior) is only partially separable. It has a flattened belly, terminating near the lower third of the tibia on a flat tendon which soon fuses with the principal tendon. (3) The deep head (M. flexor hallucis longus) is much the largest. It lies on the posterior surface of the tibia, from the popliteal line outward and downward. The belly contains much tendinous tissue, and terminates behind the distal end of the tibia on a strong round tendon. The latter receives the tendon of the tibialis posterior, passes downward in the tarsal groove, bound down by the strong tarsal fascia (Ligamentum laciniatum) and enveloped in a synovial sheath, receives the tendon of the inner head below the hock, and, a little further down, the so-called check ligament (Caput tendineum [Schmaltz]). The tarsal sheath (Vagina tarsea) begins about two to three inches (ca. 5 to 7.5 cm.) above the level of the internal malleolus, and extends about one-fourth of the way down the metatarsus. (Distention of the sheath, as in “thoroughpin,” affects chiefly its proximal end.) The check ligament resembles that of the fore limb, except that it is longer and very much weaker; it may be absent. The remainder of the tendon is arranged like that of the thoracic limb.
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.
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.
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.
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.
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.