Part 104

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.

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.