90 CLASS MAMMALIA. 



which this extension takes place. The skin of the flanks i® 

 not only carried over the arms, and distributed between the 

 phalanges of the metacarpi and fingers, but it also embraces 

 the hinder extremities : it is prolonged, more or less, in the 

 different species, between the legs, and spread to the length 

 of the tail, so as to form a surface round the animal utterly 

 disproportioned to the smallness of its body. In truth, a 

 surface of this extent could alone impart such exquisite tact 

 to the organs of touch and hearing. Spallanzani, who has 

 observed their phenomena, attributes them to a sixth sense. 



The external ears participate in this tendency to exten- 

 sion in the cutaneous system ; insomuch that sometimes, as 

 in the vespertilio auritus, there is a portion of the ears pro- 

 longed over the forehead, and partly joined together, 

 equalling in length the animal itself. They participate in 

 this tendency too, in a manner not a little singular, being 

 double in the majority of the bats. Independently of the 

 external ala of the ear, which differs from that of other ani- 

 mals only by a greater degree of extension, there is a second 

 which borders on the meatus auditorius. 



Although this little ear, or auricula*, is not positively to 

 be found except in the bats, it is not an organ of which 

 there are no traces to be discovered elsewhere. Nature 

 operates with a certain number of materials, which vary 

 only in dimension. This auricula is derived from the tragus, 

 or rather it is the tragus itself, which we might almost be 

 tempted to consider as a separate part, in consequence of 

 its extent and peculiar uses. ^ 



This susceptibility of increase in the tegumentary system 

 is manifested at the entrance of other cavities of the organs 

 of sense. In many of the cheiroptera we find the nose bor- 

 dered with crests, or foliaceous appendages, formed by a 

 duplicature of the skin. These membranes are disposed in 

 the form of a tunnel, the end of which serves for an entrance 



* The French term is " ordlhn? an excellent word for which 

 we have no equivalent. — P. 



