356 THE MUSCLES OF THE OX 



IV. MEDIAL MUSCLES OF THE TfflGH 



The sartorius arises Ijy two heads, one from the tendon of the psoas minor 

 and the ihae fascia, the other from the shaft of the ilium. The femoral vessels 

 pass between them. 



The gracilis is more extensively united with its fellow at its origin than in the 

 horse. 



The pectineus is large, and arises ])y a single head from the pubis and prepubic 

 tendon. It divides into two branches, one of which is inserted as in the horse, 

 while the other extends to the medial epicondyle of the femur. 



The adductor resembles that of the horse, but does not reach to the medial 

 condyle of the femur. 



The quadratus femoris and obturator extemus resemble those of the horse. 



The obttirator intemus has no iliac head, and its tendon passes through the 

 obturator foramen. 



The gemellus is large; some of its fibers of origin join the obturator internus 

 through the lesser sciatic foramen. - 



V. MUSCLES OF THE LEG AND FOOT 



A. DORSO-LATERAL GrOUP 



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 long digital extensor (M.' extensor digitalis longus) arises in common 

 with the peroneus tertius and the medial extensor 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 

 clown by two annular ligaments) and ends like that of the thoracic limb. 



2. The m.edial digital extensor (M. extensor digiti tertii proprius) arises in com- 

 mon 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 medial digit. 



3. The lateral digital extensor (M. extensor digitalis lateralis s. digiti quarti 

 proprius)^ arises on the lateral ligament of the stifle joint and the lateral condyle of 

 the tibia. Its tendon passes over the lateral surface of the hock, and terminates 

 on the dorsal surface of the second phalanx of the lateral digit. 



The reinforcing bands from the suspensory ligament are arranged as- in the 

 forelimb. 



4. The short digital extensor (M. extensor digitalis brevis) resembles that of 

 the horse; it is inserted on the tendon of the long extensor. 



The peroneus longus (not present in the horse) is situated in front of the lateral 

 extensor. It arises on the lateral condyle of the tibia and the fibrous band which 

 represents the shaft of the fibula. Its tendon passes downward and backward 

 over the lateral surface of the hock, crosses over that of the lateral extensor and 

 under the lateral ligament, and ends on the first tarsal bone and the proximal end 

 of the large metatarsal bone. It is enveloped by a synovial sheath. It would ap- 

 parently act as an inward rotator at the hock joint. 



The peroneus tertius is a well-developed muscle which arises on the common 

 tendon with the long and medial 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- 

 proximal end of the large metatarsal and second and third (fused) tarsal bones. 



'■ Lesbre regards this muscle as the homologue of the peroneus brevis of man and other 

 pentadactyls. 



