i84 THE ARTISTIC ANATOMY OF ANIMALS 



surface of the forearm., behind the common extensor 

 of the digits, arises, as a rule, from the epicondyle 

 (dog, cat), or from the external surface of the superior 

 extremitj' of the radius (horse). The tendon succeeding 

 to the fleshy body appears towards the lower third 

 of the forearm, and at the level of the wrist lies in a 

 groove analogous to that which in man is hollowed out 

 for the passage of the corresponding tendon at the level 

 of the inferior radio-ulnar articulation. This groove cor- 

 responds to the same articulation in animals in which the 

 ulna is well developed, such as the dog and the cat ; but 

 it belongs to the radius when the inferior extremity of the 

 ulna does not exist — for example, in the horse. Indeed, 

 in this animal the groove in question is found on the ex- 

 ternal surface of the carpal extremity of the radius. 



In the dog, the tendon is divided into three parts, which, 

 crossing obliquely the tendons of the common extensor of 

 the digits, pass to the three external digits, to be inserted 

 by blending with the corresponding tendons of the latter 

 into the third phalanges of those digits. 



Thus is explained the name of common extensor of the three 

 external digits which is sometimes given to this muscle. 



In the cat, there is a fourth tendon, which passes to the 

 index-finger, so that the name common extensor of the four 

 external digits is in this case legitimate, and the lateral ex- 

 tensor of the phalanges is also a common extensor, as is 

 the anterior extensor of the phalanges, or common extensor 

 of the digits. 



In the pig, the tendon, which is single, is inserted into 

 the external digit, for which reason it has received the 

 name of the proper extensor of the small external digit. This 

 muscle is, then, really the homologue of that which exists 

 in the human species. 



In the ox, it is called the proper extensor of the external 

 digit ; it is as thick as the common extensor. 



Finally, in the horse, the muscle is little developed. Its 

 fleshy body, thin and flattened from before backwards, 

 becomes distinctly visible only below the middle of the 

 forearm. Above, it is enclosed in a limited space, bounded 



