MYOLOGY 219 



the knee is already flexed ; it thus acts in a passive fashion, 

 which is explained by its resistance and the position which 

 it occupies in relation to these two articulations. 



Extensor Proprius Pollicis. — This muscle exists only in 

 the dog and the cat, and there in a rudimentary condition. 



It is covered by the common extensor of the toes and the 

 tibialis anticus, and passes, accompanied by the tendon of 

 this latter muscle, to terminate on the second metatarsal, 

 or the phalanx, which articulates with it. When the first 

 toe exists in the dog, it is inserted into this by a very 

 slender tendon. 



Extensor Longus Digitorum (Fig. 83, 9 ; Fig. 84, 7 ; 

 Fig. 85, 5, 6 ; Fig. 86, 4 ; Fig. 87, 12 ; Fig. 88, 7).— It is also 

 called by veterinarians the anterior extensor of the phalanges. 



In the dog and the cat this muscle is to be seen in the 

 space limited behind by the peroneus longus and in front by 

 the tibialis anticus. Above it is covered by this latter. In 

 the lower half of the leg, it is also in relation, on the inner 

 side, with the tibialis anticus ; but behind it is separated 

 from the peroneus longus by the external surface of the 

 shaft and inferior extremity of the tibia. This arrange- 

 ment, besides, recalls that which is found in man, the 

 peroneus longus of the latter diverging in the same way, at 

 this level, from the common extensor, and leaving exposed 

 the corresponding portion of the skeleton of the leg. 



This muscle, fusiform in shape, arises at its upper part 

 from the external surface of the inferior extremity of the 

 femur, then its tendon passes into a groove hollowed on 

 the external tuberosity of the tibia. The fleshy body which 

 succeeds is directed towards the tarsus, but before reaching 

 it is replaced by a tendon. This tendon, at the level of the 

 metatarsal bones, divides into four shps, which pass towards 

 the toes, and are inserted into the second and third 

 phalanges of the latter. 



In the horse it covers, to a great extent, the tibialis 

 anticus, so that it is the latter which forms the large fusi- 

 form prominence especially noticeable in the middle region, 

 to which the contour of the anterior surface of the leg 

 is due. 



