170 PHILOSOPHY OF ZOOLOGY. 



effects produced on their skin by the air. These may arise 

 from the resistance of that fluid, or other causes with which 

 we are but imperfectly acquainted. Bats appear to possess 

 this exquisite sensibility of touch, independent of habit or 

 experience. SPALLANZANI has observed these animals, 

 even after their eyes had been destroyed, and ears and nos- 

 trils shut up, fly through intricate passages without strik- 

 ing against the walls, and dexterously avoid cords and lines 

 placed in their way. The expanded membrane of their 

 wings is probably the organ which, in such cases, receives 

 the impressions produced by a change in the resistance, mo- 

 tion, or perhaps temperature of the air. The susceptibility 

 of being acted upon by these agents, which exercise a feeble 

 influence over us, is a condition natural to these animals, 

 and necessary to enable them to find their way in the dark 

 caverns in which they dwell. It cannot therefore be re- 

 garded as one of those resources employed in time of need, 

 in the case of bats, although it appears to be such in 

 blind people. Man naturally moves but little in the dark, 

 so that he doe&not require such susceptibility. It is, how- 

 ever, fortunate that his body is susceptible of acquiring it 

 in the time of need. 



The sense of touch appears, in man, to be able to obtain 

 nearly all the information, with regard to external objects, 

 which it is capable of receiving. In a few instances, the 

 lower animals surpass us in the delicacy of this sense, as the 

 bat, which is warned, indirectly, by its aid, of the presence 

 of bodies, previous to coming in contact with them. The 

 feelers of insects are likewise better adapted for exploring 

 the condition of the surface of bodies, than any organ 

 which we possess. But, in all these cases, the sensibility of 

 touch is limited to particular qualities, or confined within 

 narrow bounds. The human hand, on the contrary, by its 





