io8 THE ARTISTIC ANATOMY OF ANIMALS 



study in the case of the horse. The articulations of the 

 bones of the tarsus, and of these with the metatarsus, do not 

 offer any interest with regard to mobihty, this being almost 

 wholly absent at that level. 



The leg and the astragalus, in a general way, are placed in 

 contact by such articular surfaces that the resulting joint, 

 which is a true hinge, permits movements of flexion and ex- 

 tension only. Indeed, as we have indicated above, the tibia 

 is furnished, on the inferior surface, with a crest that fits into 

 the deep groove which is situated on the corresponding 

 surface of the astragalus. 



During flexion, the anterior surface of the foot tends to 

 approach the anterior surface of the leg, the angle formed 

 by these two segments becoming more and more narrowed. 

 The displacement in the opposite direction characterizes 

 extension. 



In other quadrupeds, the articulations which bind together 

 the bones of the tarsus possess a little more freedom of move- 

 ment. The shape of these bones, and particularly the shape 

 of the surfaces of the astragalus, which are in contact with 

 them, allow movements in this region, in the case of the dog 

 and cat, which, without being so extensive as those of the 

 human foot, in the subastragaloid articulation, neverthe- 

 less, recall the mobility which we find in the human species 

 at this level — that is to say, rotation, abduction, and 

 adduction of the foot. 



As for the articulations of the metatarsus with the 

 phalanges, and of the phalanges with one another, they re- 

 semble those of the anterior limb too closely that it should 

 be necessary to study them here. Such a study would 

 be, in this case, but a repetition (see p. 76, a description of the 

 articulations in question). 



THE HEAD IN GENERAL, AND IN SOME 

 ANIMALS IN PARTICULAR. 



When we compare, by the examination of one of their 

 lateral aspects, the skull of man and the same region in other 

 mammals, it is easy to observe that the relati\-e develop- 

 ment of the cranium and face is entirely different. In the 



