64 TEXT-BOOK OF ZOOLOGY 



4. The bat catches its prey while flying, consequently the mouth is 

 widely cleft. (Compare the swallow.) 



5. The teeth have the app'earance of rows of needle-points. The 

 molars have pointed cusps. They, as well as the long dagger-shaped 

 canines, are able to bore with ease through the hard wing-covers and the 

 armour of larger insects, from which blunt teeth would glide off. The 

 animal uses its teeth neither for gnawing nor grinding (like a herbi- 

 vorous animal), but merely for biting and boring. Since the points of 

 the teeth of one set are received in the interstices of the other set, the 

 crowns are not worn down by use. (Compare with cat.) 



6. The animal diet corresponds to the short intestine, only three times 

 as long as the body. 



7. The neck is very short. A long neck, by which the head is 

 enabled to move in all directions (compare the stork), would be useless 

 to a bat, which in the pursuit of prey during flight can easily turn head 

 and body together in any direction it pleases (compare the swallow). 



8. With the nature of the food is also correlated the small size of the 

 animal. A large animal could not obtain enough insects to satisfy itself. 



C. Hibernation of Bat. 



It would be difficult, if not impossible, for a bat to exist through the 

 winter, unless it adopted the habit of hibernating ; for it cannot pursue in 

 their hiding-places those insects which live through the winter, nor is it 

 able to lay up a store of provisions for that season like the squirrel (why 

 not?), nor are its powers of flight of so enduring a nature as to enable it 

 like birds to migrate to warmer countries. Accordingly, when the raw 

 weather sets in, the bat seeks out as protected a hiding-place as possible, 

 though one not too dry (why?), such as a mountain cave, a cellar, a loft, 

 a ruined building, the hollow trunk of a tree, and so on. There these 

 animals may be met with often in crowds, hanging up by their feet, 

 unconscious, stiff and motionless. In this condition the heat of the 

 body drops from 35° C. to 14° C. (95° F. to 57° P.) ; the pulse only beats 

 about once every three minutes, and the respirations are rare and hardly 

 perceptible. But as soon as Nature reassumes her garment of green and 

 the thousands of different kinds of insects reappear, the bat, too, 

 reawakens to a new life. Let us now inquire how it has been able to 

 tide over the long period of cold and fasting. 



1. If the body-heat of an animal, especially a warm-blooded one, sinks 

 below a certain minimum, the creature must perish. In the case of the 

 bat this issue is prevented by several means : 



(a) An Uncommonly Thick Hairy Covering. — The number of .hairs 

 covering the tiny body has been computed at about 1J millions. These 



