BATS. 29 



in the bright rays of the sun, it was intended that the bat should 

 come forth, to continue the war where she had left off, and, 

 with equal ardour, pursue and lessen the number of those that 

 fly and dance in the moon-beams. Indeed, it might almost be 

 received as an unexceptionable axiom, that whatever office is 

 fulfilled by an animal of any particular class, nearly all the 

 other classes contain some species which afford good and effi- 

 cient assistance in performing the same task, though the mode 

 and time for going about it may differ materially. Still, how- 

 ever, the work is done in every place and at every hour -, thus, 

 the air is cleared from the swarms of tormenting insects by 

 the bat, the swallow, the carp, the toad, the dragon-fly, and 

 the spider, while the earth is swept clean from dead or decayed 

 matter by the hyaena, the vulture, the shark, the crocodile, the 

 crab, the carrion-beetle, and the slug. 



" During its winter torpidity," says Captain Brown, " the 

 circulation of its blood is so slow, that its motion is hardly 

 perceptible. From some experiments of Spallanzani, it would 

 almost appear that a total suspension of vital energy takes 

 place in animals, during this state of torpor, for he kept a torpid 

 bat four hours in carbonic acid gas, the thermometer marking 

 twelve degrees ; yet it continued to live in this gas, which 

 is so very deleterious, that a bird and a rat, which he exposed 

 to its influence at the same time, perished instantaneously."* 



" It makes its appearance, after its short period of torpidity, 

 as early as the middle of March, and does not wholly retire into 

 a state of undisturbed hibernation until the winter has decidedly 

 set in: its torpidity, therefore, can hardly be said to continue 

 more than from two to three months. Their final retirement does 

 not depend exclusively upon temperature ; for although before 

 the severe frosts set in, they continue to fly even when it is 

 below the freezing point, they do not again appear until the 

 above time, notwithstanding the thermometer, as Mr. Jenyns 

 has observed, may have often risen considerably above 50 

 Fahrenheit. This peculiarity is of easy solution. The bat's 

 * Sketches and Anecdotes of Quadrupeds (Glasgow), 1831, p. 97. 



