OSTEOLOGY AND ARTHROLOGY 



89 



name we adopt in conformity with usage, but which we 

 cannot but regret, as in human anatomy the ham is the 

 region of the posterior surface of the knee. 



The general arrangement of the region of the digits of the 

 posterior hmbs in birds, presents some points of interest. 



We shall merely say with regard to the metatarsus, that 

 it is formed by a single bone, which in the cock is furnished 

 towards its inferior third with a pointed process, the spur. 

 At the inferior part, there is, however, found another, which 

 is but very slightly developed, and with which the first 

 phalanx of the innermost toe articulates. 



The toes are, in the majority of species, four in number :* 



Fig. 47. — Posterior Limb of the Horse placed in the Position which 



IT SHOULD occupy IF THE AnIMAL WERE A PLANTIGRADE : LeFT LiMB, 



External Surface. 



I, Tibia; 2, astragalus; 3, calcaneum ; 4, metatarsus ; 5, first phalanx; 

 6, second phalanx ; j , third phalanx. 



an internal, which is directed backwards, and corresponds to 

 the great - toe ; the others are directed forwards. This 

 arrangement is constant in grallatores (wading birds), galli- 

 nacese t (domestic fowls), and raptores (birds of prey). 

 In climbing birds (parrots, woodpeckers, and toucans), the 



* In spite of the fact that the custom is to dssignxte the terminal por- 

 tions of the foot of birds by the nam 3 of digits, we prefer to employ here 

 the terms foot and toes. In adopting tliis decision we believe we are 

 acting according to a more didactic method. Homology of names should, 

 in our opinion, always accompany homology of regions. 



f With regard to the gallinaceae, we must add that in certain varieties 

 the number of toes is five ; those which are directed forwards are three 

 in number ; the internal one which passes backward, is double. The two 

 toes which are the subject of this special arrangement are placed very 

 close together, and are nearly always superimposed. This condition is 

 found in the Houdan and Dorking breeds. 



