GENERAL CHARACTERS OF MAMMALIA. 23 



11. When the extremities are designed only to sustain the 

 body and to move it over the surface of the ground, they 

 should possess great solidity, and be at the same time slender 

 towards the end, that they may be the lighter ; now, long and 

 flexible fingers or toes would be injurious to this solidity, and a 

 considerable number of these organs would augment the weight 

 of the foot without any advantage; therefore, with those animals 

 whose four feet only serve them in moving, (walking or run- 

 ning) the fingers or toes are generally but two or three in num- 

 ber, short, slightly flexible, and completely enveloped at their ex- 

 tremity, by nails, which protect them. 



12. When the extremities are designed chiefly for touch, and 

 the prehension of objects, it is altogether different ; they are then 

 very flexible, terminated by five fingers which are long, well 

 separated from each other, and so moveable that one of them, at 

 will, can change position, and apply itself against the others, like 

 a pair of plyers or pincers ; the nail is in this case flat, and only 

 covers the back of the end of the fingers, the lower surface of 

 which resembles a soft cushion ; and the whole hand can move 

 upon the fore-arm, to direct itself inwardly or outwardly, as 

 occasion may require. 



13. The hoofs of the horse may be taken as an example of 

 the mode of conformation of extremities, which are designed 

 only for moving the animal ; and the hand of man, as an example 

 of the conformation of these same organs when they are designed 

 for prehension and touch. But between these extremes there are 

 a great many intermediate degrees, and with a great many of the 

 mammalia, the paws serve at once the purposes of progression, 

 prehension, and touch, and discharge best, either one or other of 

 these functions, according as their conformation most approaches 

 to one or the other of the two modes of structure, just spoken of. 



14. The mammalia that climb best, generally have paws more 

 or less like our hand, and suited for seizing hold of objects ; there 

 are some, however, that by the assistance of very sharp nails, 



11. What are the characters of the extremiiios when they are designed 

 merely to sustain the animal in walking? Have they many long flexible 

 toes? How imny toes has an animal that usually goes on all fours? 



12. What are the characters of the extremities when designed for touch 

 or prehension ? 



13. Give examples of the different conformation of extremities according 

 to their uses ? 



14. What are the means or instruments provided for those mammalia that 

 climb? Do any of this cla-s ever assist themselves in climbing by any 

 other means than their hands or feet? 



