iv.] SKELETON OF UPPER LIMB. 169 



Very rarely, as in the Crocodile, the two proximal bones 

 may be so much longer than the others as to take on some- 

 what the character of "long bones," and to constitute by 

 themselves another limb segment. 



1 8. The BONES OF THE FIRST ROW of the carpus, except 

 the pisiforme, may be represented by one single bone, as in 

 Pteropus. 



" Inasmuch as the scaphoides articulates with the radius, it 

 has a character which is constant The distinctness which it 

 possesses in man is by no means universal. Thus the sca- 

 phoid coalesces with the lunare in the Carnivora and many 

 other Mammals, and also probably in the Crocodiles. It 

 unites with the cuneiforme in addition in Pteropus. It may 

 coalesce with the trapezium, as in the Three-toed Sloth. It may 

 become a considerably elongated bone, as in the Crocodile. 



On the outer (radial) side of the scaphoid we often find a 

 small ossification of a tendon, or sesamoid ossicle, corre- 

 sponding with that sesamoid ossicle of the ulnar side, which is 

 counted as a carpal, and called the Pisiforme. 



This radial sesamoid ossicle is found even in Apes, but it 

 attains its maximum in the Mole, where it strengthens and 

 broadens the hand for digging. It is found even in some 

 Reptiles, as e.g. in Emys europea. 



An extra bone which exists in many Vertebrates, but not in 

 man (and which goes by the name of os centrale, or interme- 

 dium}, is most probably a dismemberment of the scaphoid. 

 It is present and distinct in the Apes, except the very highest, 

 and many other forms, including most Reptiles and Batra- 

 chians. The form of the scaphoid in Emys europea seems to 

 show that the centrale is a dismemberment of the scaphoid, 

 as indeed does its position in the Orang. 



This conclusion is indicated by the occasional ossification 

 of the scaphoid from two centres, in the class Mammalia. 



The centrale may form a very large and conspicuous part 

 of the carpus, to the abortion of any representative of the 

 trapezium. This, e.g., is the case in the Crocodile ; and if 

 the centrale be a dismemberment of the scaphoid, then, con- 

 sidering the length and size^of the undoubted scaphoid or 

 scapho-lunar bone in the Crocodile, the equivalent of man's 

 scaphoid forms alone the larger half of the carpus in that 

 reptile. Again, the centrale may form a singularly con- 

 spicuous part, as in the Chameleon, where it is surrounded 

 by the more distal bones of the carpus, which have re- 

 spectively coalesced with their adjacent metacarpals. 



