1 72 ELEMENT A RY ANA TO MY. [LESS. 



larger than it is in man, and it may, as in the Three-toed 

 Sloth, coalesce with the os magnum. 



The os magnum may be much smaller relatively than in 

 man (as e.g. in the Bear and Hare) ; or relatively larger (as 

 in the Hyrax) ; or it may seem to abort altogether, as in 

 Birds. Compared with the bones of the second row only, it 

 may be, as in the Horse, a more predominant bone than it is 

 in man. 



The undivided state in which the unciform bone exists in 

 man is universal in his class. 



It may, however, be represented by two distinct bones 

 corresponding with and supporting the fourth and fifth meta- 

 carpals, as in Chelonia, Chelydra, and Salamandra. There 

 may be no bone whatever capable of identification with it, as 

 in Birds. It may be much smaller or larger relatively than 

 it is in man. 



An additional ossicle not found in man may be present in 

 the ligament connecting the trapezium and unciform bones. 

 This is the case in the Potto (Perodicticus). 



20. The distinctness and development which the META- 

 CARPUS or middle segment of the hand attains in man are 

 characters which are normal. The somewhat opposed posi- 

 tion of the first metacarpal in him is only found in a few 

 Mammals besides in Monkeys and Lemurs. 



The metacarpals, however, may fuse with the distal carpals 

 the trapezium with the first metacarpal, as in the Three- 

 toed Sloth, or all five with the corresponding carpals, as in 

 the Chameleon. 



A more complete opposition may obtain, however, than that 

 which exists between the first and the other metacarpals in 

 man ; as is shown by the Chameleon, in which the three radial 

 metacarpals are as strongly as possible opposed to the two 

 ulnar ones. 



In the number of these bones and their sub-equality of 

 development man agrees with many Vertebrates above 

 Fishes. Nevertheless, the number may be much reduced, 

 and the proportions of the several bones may vary in differ- 

 ent modes. 



Thus there may be but a single metacarpal (the third), with 

 rudiments of two others, as in the Horse ; or there may be but 

 a single bone, which consists of the third and fourth fused 

 together, as in the Sheep, Deer, &c. 



Again there may be but two, the second and third, with 

 another rudimentary metacarpal (which answers to man's 



