110 MEMBERS, AND ORGANS OF SENSATION. 



radius can no longer turn upon the ulna ; and is so closely 

 united to it, that it can no longer be distinguished ; this is also 

 the case with fhejibula, which is joined with the tibia among the 

 hoofed quadrupeds. The conformation of the hand and foot 

 vary greatly in this class of animals, according as these mem- 

 bers are intended to serve for walking, for prehension, for 

 swimming, or for flying. These curious modifications have been 

 elsewhere dwelt upon (ANIM. PHYSIOL. Chap. XII.), and con- 

 sequently it is not necessary for us to describe them here ; we 

 shall only add, that the number of fingers never exceeds five, and 

 diminishes in proportion as the four members are devoted more 

 exclusively to walking. 



92. Organs of Sensation. The degree of flexibility of the 

 fingers, and the nature of their movements, influence their use, 

 not only as organs of locomotion and of prehension, but also as 

 instruments of the sense of feeling. When they cannot take hold 

 of the objects to feel them, and when the hand cannot mould it- 

 self, as it were, upon their form, feeling becomes necessarily very 

 imperfect ; and that which tends to deaden it still more, is when 

 the nail, instead of leaving the end of the finger in great part 

 uncovered, completely envelopes it, and takes the form of a hoof. 

 Now the greater or less perfection of this sense influences, in its 

 turn, the development of the intellect ; and it may be said with 

 truth, that in the immense majority of cases, if not in every 

 instance, the faculties of Mammalia are elevated in proportion 

 as their members are better formed to seize and to feel. 



93. The organs of the other senses, in all the animals of this 

 class, present nearly the same mode of organisation as in Man. 

 In those which are remarkable for the delicacy of their smell (as 

 is the case among the Carnivora more than any others the Dog, 

 for example), the nasal bones and the frontal sinuses are increased 

 very considerably, and the spongy bones, which project within 

 the olfactory cavity, are much more developed. (ANIM. PHYSIOL. 

 506) . It is easy to perceive the usefulness of these differences, 

 as they tend to give to the lining membrane, which is the seat of 

 this sense, a more extended surface. 



94. The Eyes are in general proportionally larger among the 



