148 BIOLOGY. [BOOK n. 



an almost uniform exterior temperature. 1 On the contrary, birds, 

 whose nutritive movement is intense and rapid, succumb very 

 quickly. One day of abstinence kills a sparrow, three days a 

 thrush, &c. The same law is verified in the same animal organ- 

 ism, according to the various ages. Thus, in middle life, man can 

 resist complete abstinence for one or two weeks. The child 

 succumbs sooner, and the old man much later. 



Everything which retards the quickness of the nutritive 

 exchanges helps to support abstinence ; for example, repose in 

 bed, sleep, and the substances which provoke it. 



Without having for the animal the primordial importance 

 which it has for the plant, solar light is nevertheless a powerful 

 excitative of life in the animal kingdom also. Moreover, absti- 

 nence is better supported in darkness. Eight miners shut up 

 for thirty-six hours in a coal-pit without food said they had 

 not suffered from hunger. 



Nevertheless, in all animals death is sooner or later the 

 result of abstinence, and in all, it takes place when the organism 

 has lost a part of its weight, always perceptibly the same for all 

 the species. If the animals known as cold-blooded live much 

 longer than others, it is only because their diurnal loss is normally 

 much less. They expend less, and consequently their capital is 

 not so soon exhausted. 



1 Cl. Bernard, Lcyom sur Us Proprietes des Tissus Vimnts, p. 49. 



