OSTEOLOGY AND ARTHROLOGY 



43 



Man. 



A. Long abductor 

 of the thumb, 

 and short ex- 

 tensor of the 

 thumb. 



B. First and 

 second external 

 radials (extensor 

 carpi radialis lon- 

 gior and brevior). 



C. Long extensor 

 of the thumb. 



Dog. 



D. Special exten- 

 sor of the index 

 finger and the 

 common exten- 

 sor of the 

 fingers. 



E. Special exten- 

 sor of the little 

 finger. 



F. The posterior 

 ulnar {extensor 

 carpi nlnaris). 



A. Long abductor of the 

 thumb and short ex- 

 tensor of the thumb 

 united as one muscle, 



the oblique extensor of 

 the metacarpus.* 



B. The two radials blended 

 superiorly, distinct 

 inferiorly ; this is the 

 anterior extensor of the 

 metacarpus. 



C. Long extensor of the 

 thumb and special ex- 

 tensor of the index 

 finger united superi- 

 orly. These muscles 

 pass in the following 

 groove. 



D. Common extensor of 

 the digits and the two 

 preceding muscles. 



Horse. 



A. Oblique extensor of the 

 metacarpus, the homo- 

 logue of the long ab- 

 ductor of the thumb 

 and the short extensor 

 of the thumb, united as 

 one muscle. 



B. The radials represented 

 by a single muscle, the 

 anterior extensor of the 

 metacarpus. 



C. The long extensor of 

 the thumb and the 

 special extensor of the 

 index are absent. 



D. Anterior extensor of the 

 phalanges, the homo- 

 logue of the common 

 extensor of the digits. 



E. Extensor of the third, 



fourth, and fifth digits, 



or the lateral extensor of 



the digits, the homo- 



logue of the special ex- 

 tensor of the little finger. 

 There does not exist on the forearm a groove for the 



posterior ulnar muscle, or external flexor of the 



metacarpus. 



E. Lateral extensor of the 

 phalanges, the homo- 

 logue of the special 

 extensor of the little 

 finger. 



represented in this region by a tongue-like process of bone ; 

 and in such cases the groove is situated in front of this 

 process, at the level of the line of coalescence, which there 

 represents the articulation. 



It is also useful to note, with reference to the groove F, 

 in which passes, in man, the tendon of the posterior ulnar 

 muscle, that, when the forearm is in pronation, the radius 

 alone being displaced, we can only see this groove on the 

 surface which looks backwards ; and that it is then separated 

 from the groove which contains the tendon of the special 

 extensor of the little finger by an interval equal to the thick- 



* The words printed in itaUcs are the names used in veterinary 

 anatomy. 



