76 THE ARTISTIC ANATOMY OF ANIMALS 



We will remember that in the ox and the horse the region 

 of the wrist is called the knee. 



In flexion, the hand is bent backwards ; in extension it 

 is carried forwards. These two movements take place 

 especially in the radiocarpal and intercarpal articulations. 

 In the first of these articulations, it is the superior row of 

 the carpus which glides backwards and forwards on the 

 corresponding articular surface of the forearm. In the 

 second articulation, it is the second row which moves ; 

 gliding on the inferior articular surfaces of the row above 

 it. This inferior row carries the metacarpus with it ; for 

 the carpo-meta carpal articulation is much less mobile than 

 either of the other two. 



In flexion, the articular surfaces are separated from one 

 another in front ; and the changes of form which result 

 from this are noticeable on the anterior surface of the 

 ' knee.' Moreover, at that moment this region contrasts 

 markedly in its outlines with the parts above it and below 

 it — that is to say, with the corresponding surfaces of the 

 forearm and of the canon bone. 



As for the lateral movements, by which the hand is 

 inclined outwards and inwards in its movements at the 

 wrist, they exist to an appreciable extent in the cat and the 

 dog only ; in order to understand this, it is enough to com- 

 pare the shape of the articular surfaces of this region in 

 carnivora and the horse, for example. In the latter, those 

 surfaces are almost plane ; in the cat, on the contrary, the}/- 

 are curved (inferior surface of the forearm, concave ; superior 

 border of the carpus, convex). These latter, then, are, in 

 form, similar to those which exist at the same level in the 

 human being ; this explains the possibility of analogous 

 movements of the whole hand — that is to say, of the mo\-e- 

 ments of abduction and adduction. 



The Metacarpo-phalangeal Articulations. — With regard 

 to the mobility, it is in these articulations, as in those of the 

 wrist — that is to say, although in all quadrupeds the first 

 phalange? can be flexed and extended on the metacarpus, 

 it is only in the cat and dog that lateral movement is possible. 

 Indeed, in the horse, in which the principal metacarpal ter- 



