284 TRESPASSERS UPON THE AIR. 



tended the surface is very large in proportion to the 

 weight of the animal. 



There is at least one genus of Bat which possesses 

 still further means of lightening the body. 



" In the genus Nycteris a curious faculty is ob- 

 served, namely, the power of inflating the sub- 

 cutaneous tissue with air. The skin adheres to the 

 body only at certain points, where it is connected by 

 means of a loose cellular membrane. It is therefore 

 susceptible of being raised from the surface on the 

 back as well as on the under parts. These large 

 spaces are filled with air at the will of the animal, by 

 means of large cheek-pouches, which are pierced at the 

 bottom, and they communicate with the subcutaneous 

 spaces just mentioned. 



" When the animal, therefore, wishes to inflate its 

 skin, it inspires, closes the nostrils, and then, con- 

 tracting the cavity of the chest, the air is forced 

 through the openings in the cheek-pouches under the 

 skin, from whence it is prevented from returning 

 by means of a fine sphincter, with which those open- 

 ings are furnished, and by large valves on the neck 

 and back. 



" By this curious mechanism, the Bat has the power 

 of so completely blowing up the spaces under the 

 skin, as to give the idea, as Geoffrey observes, of a 

 little balloon furnished with wings on head and feet." 

 The foregoing passage is taken from Mr. Bell's 

 article on the Cheiroptera, in the " Cyclopaedia of 

 Anatomy and Physiology." 



The reader will remember that some of the sea- 

 birds have the same capacity of inflating a series of 



