THE MANUS. 



[CHAP. 



R 



Among the animals constituting the order EDENTATA 

 there is great diversity in the structure of the fore-foot. 

 They agree, however, in wanting an os centrale, and (with 

 the exception of Manis) in the presence of distinct scaphoid 

 and lunar bones. 



In the existing Sloths the whole manus is long, very 

 narrow, habitually curved, and terminating 

 in two or three pointed, curved claws, in 

 close apposition with each other, incap- 

 able, in fact, of being divaricated, so that 

 it is reduced to the condition of a hook, 

 by which the animal suspends itself to 

 the boughs of the trees among which it 

 lives. 



The carpus is small, and articulates by 

 a smooth rounded surface with the lower 

 end of the radius. In the Three-toed 

 Sloths (genus Bradypus) it consists of dis- 

 tinct scaphoid, lunar, and cuneiform bones 

 in the first row, but usually of only two 

 bones in the second row, the unciform, 

 and a connate magnum and trapezoid, the 

 trapezium being generally ankylosed to 

 the rudimentary first metacarpal. 1 There 



FIG. 106. Bones of the n j j T u j- i 



right manus of the is a small rounded pisiform, but no radial 

 tepu*s*didactyius\l- sesamoid. The first and fifth metacarpals 



are present in a rudimentary condition 

 but bear no phalanges. The three middle digits are nearly 

 equally developed. The proximal phalanges are extremely 

 short, and soon become ankylosed to the ends of the 

 metacarpals, so that in adult animals one of the usual bones 

 of the digit appears to be entirely wanting. The middle 

 1 See "Journal of Anatomy and Physiology," vol. vii. p. 255. 



n 



