1 70 ELEMENTAR Y ANA TOMY. [LESS. 



As has been already said, the semi-lunar bone may coalesce 

 with the scaphoid in many animals, e.g. the Dog. It may, 

 on the contrary, unite with the cuneiforme, as in the Sala- 

 mander and Triton, and probably in Birds. It seems also to 

 be generally absent as a distinct bone in Reptiles other than 

 Chelonians. Thus its distinctness in man is a rather ex- 

 ceptional character. 



The separate and well-developed condition of the cunei- 

 forme in man is one which characterizes it generally, it being 

 one of the constant carpal bones ; the only noteworthy devia- 

 tions are that, as just said, it may coalesce with the lunare, or 

 even with the scaphoid also, as in Pteropus ; or that it may 

 be-very considerably increased in length, as in the Crocodile. 

 It may be relatively larger than in man, as in the Turtle ; 

 or smaller, as in the Mole. 



The inconstancy of the pisiform* is a consequence of its 

 being really no true carpal, but only an accessory sesamoid, 

 like the radial ossicle spoken of in noticing the scaphoid. 

 Thus it is often absent, as in many Cetacea, the Sirenia., 

 Birds, many Reptiles, and all Batrachians ; while it is very" 

 small in Bats, Seals, and others. It may be much larger and 

 longer relatively than in man, as e.g. in the Carnivora. 



19. The BONES OF THE SECOND ROW are by no means so 

 constant in number or development as are those of the first 



<s. 



FIG 144. Left Hand of Chameleon, showing the opposition between thetwoulnar 

 and the three radial digits. 



tn l m$, the five complex bones formed of the union of each metacarpal with the 

 corresponding distal carpal bone ; r, radius ; n, ulna ; i, ulnar proximal carpal 

 bone ; 2, radial proximal carpal bone ; 3, intermedium or centra'e. 



row. They may coalesce with the metacarpals, as is the case 

 in the Chameleon. 



The importance and size of the trapezium in the human 

 carpus, owing to the relation it bears to the development of 

 man's thumb, are very different from what we see in some 

 members of man's class, and even order. 



