176 THE ARTISTIC ANATOMY OF ANIMALS 



is to say, arranged in these two regions — that we proceed 

 to study these muscles in quadrupeds. 



Anterior and External Region 



Supinator Longus. — We know that this muscle, which 

 is especially a flexor of the forearm on the arm, plays, not- 

 withstanding the name which has been given it, a part of 

 but little importance in the movement of supination. 



It acts slightly, however, as a supinator, for, being very 

 oblique downwards and inwards at the time of pronation, it 

 is able, while tending to resume its vertical direction, to 

 carry the radius outwards ; it places, in fact, the forearm 

 in a position midway between pronation and supination. 



We have just recalled these details, in order that it may 

 be more easy to understand why it does not exist in animals 

 in which the radius and ulna are fused together (horse, ox) ; 

 and why, on the other hand, we find traces of it in the cat 

 and the dog, in which the radius — to a slight extent, it is 

 true — is able to rotate on the ulna. This displacement 

 being a little more considerable in the felide, the long supi- 

 nator is a little further developed than it is in the canine 

 species ; but, notwithstanding, it is only rudimentary. 



The long supinator arises, above, from the external border 

 of the humerus ; thence, in the form of a very narrow 

 fleshy band, it passes obliquely downwards and inwards, 

 to be inserted into the inferior part of the internal surface 

 of the radius. 



It assists in turning the radius outwards and placing it 

 in front of the ulna, the movement of supination being 

 capable of being but little further extended. 



First and Second External Radial Muscles: Extensor 

 carpi radialis longior and hrcvior (Fig. 73, 8 ; Fig. 74, 8, 9 ; 

 Fig. 75, 8, 9). — Fused together, these muscles form by their 

 union what veterinary anatomists call the anterior extensor of 

 the metacarpus. But we should add that these two muscles 

 are united so much the more intimately as we examine 

 them in passing successively from the cat to the dog, pig, 

 ox, and horse. Thus, in the cat they are often distinct ; in 



