BATS 65 



hairs, moreover, display a quite peculiar structure, not consisting, as in 



most other animals, of tubes of equal thickness, but, like the stalks of 



certain grasses, of conical and funnel-shaped segments. 



On account of the roughness of their surface, these hairs 



cling to each other more tightly than smooth ones, so that 



parts of the body are not so easily laid bare by a draught 



of air. 



(b) The flying membrane, which enfolds the body like 

 a mantle, likewise forms a protection against an excessive 

 loss of body-heat, since the air enclosed within it acts as a 

 bad conductor of heat. 



2. Although during its winter sleep the bat is suspended 

 like a corpse, life is by no means extinct in the interior of 

 its body. The lungs, the heart and the other organs 



continue their work slowly but uninterruptedly. Now, even HAIR ~ F LONG . 

 the least amount of work can in the animal body only be EARED BAT. 

 performed by the combustion of food material (see p. 6). * ag times). ^ 

 Consequently the bat, from the superabundance of its food 

 during the mild seasons, stores up, as in a larder, a supply of such 

 material in its body, more especially in the form of fat. This fat by 

 degrees enters the circulation, and is conducted thence to all the organs 

 in which it undergoes combustion. In this manner the needful quantities 

 of heat and force are continually produced afresh, so that, though the 

 animal machine works slowly, it is not brought to a standstill. (What 

 would happen if the animal, during its winter sleep, breathed as deeply 

 and as often as during the period of its greatest vital activity ?) 



3. The distribution of bats is rendered explicable from their mode of 

 life. The closer we approach the pole, the greater becomes the diminution 

 in insect life. In cold countries the animals, even during the warmer 

 months, would scarcely be able to find sufficient food, much less be in a 

 position of laying up a store within their body for the winter. During 

 cold and long winters they would in such countries inevitably perish 

 from loss of heat or want of food would, in fact, either freeze or 

 starve. Accordingly we do not meet with bats beyond the sixtieth degree 

 of north latitude ; but their true home is in the warm South, with its 

 abounding insect life. 



D. The Bat in its Relations to Man, and its Importance in the 

 Economy of Natter e. 



1. In popular superstition bats, from their noiseless flight and their 

 nocturnal mode of life, were once considered as evil spirits, and still at 



5 



