522 MAMMALIA. 



femoral memic senses of the Bats are of an astonishing extent and 



which arr 



It /'general the ears are large, widely open, and the perception 



cox sounds perfect. With regard to smell, it is extremely delicate. 

 In a number of species the entrance to the nostrils is covered by 

 membranous folds called nasal-leaves, which endow the olfactory 

 organ with a singular power. Lastly, the sense of touch is 

 exquisite ; a circumstance that cannot surprise us when we con- 

 sider the wide extent of their hands. 



It is to this exceptional delicacy of touch that must be attri- 

 buted the ease with which Bats fly about in their dark retreats 

 without striking against the angles, rocky projections, or other 

 objects. Spallanzani instituted experiments which were decisive 

 in this respect. The celebrated physiologist destroyed the vision 

 of several specimens, and on leaving them alone he saw them fly 

 around the room without betraying the slightest hesitation, or 

 without striking their heads against the furniture or the ceiling ; 

 in a word, without the deprivation of sight having changed in the 

 slightest degree their conditions of existence. 



This fact induced Spallanzani to declare that Bats are endowed 

 with a sixth sense, which informs them of the proximity of solid 

 bodies. But such an explanation is unnecessary. "When we are 

 aware of the prodigious sensibility of the tactile organs in these 

 animals, we may admit that they are affected by certain movements 

 of the air which are imperceptible to us, and that Bats can thus 

 be rendered conscious of the proximity of a body by the obstruction 

 to the eddies and currents of air displaced by them in their flight. 

 ^ In cold and temperate regions Bats hybernate. They are then 

 absolutely insensible, and may be handled, shaken, and even 

 thrown in the air, without betraying the least movement. But 

 if they are held for some time in the hands, or near a fire, under 

 the influence of the heat they rapidly show signs of animation. 



During the period of torpidity the vital functions are executed 

 feebly, but they are not altogether abolished. They cannot dis- 

 pense with nourishment during this portion of their existence, 

 but as they are incapable of taking food, they devour their own 

 substance, the fat that has accumulated in their bodies during 

 the period of activity. In this way is explained their emaciation 

 at the termination of their winter sleep. \ 



