S On the Action exen 



vised ly Caloric 



Such are the. results which I obtained by trying the action 

 of caloric on insects : I shall here add what I observed in 

 regard to frogs, reserving for another occasion my experi- 

 ments on other animals. 



It is well known ihat Spallanzani several times reduced 

 frogs to a state of torpor even after depriving them of their 

 blood, heart, &c, and recalled them to life. In repeating 

 the curious experiments of that philosopher, I thought pro- 

 per to make the following variations : — I separated the thigh9 

 of a frog by two cuts, and then buried them both in pounded 

 ice. I in like manner took the heart, still palpitating, and 

 immersed it also in ice. At the end of an hour all these 

 parts appeared to me to be exceedingly torpid and stiff: the 

 heart not only had lost all motion, but on touching it with 

 a pin it seemed as rigid as the rest. I threw one of the 

 thighs into water which was at -f- 20°: it manifested no 

 sensible motion, and was also entirely pale. I exposed the 

 other thigh slowly to caloric : it retained its colour, and 

 even showed some signs of irritability. In the last place, 

 the heart, an organ highly irritable, having been slowly ex- 

 posed to heat, resumed its motion, which was not weakened 

 and did not cease till an hour after it had begun to move. . 



But it is still more remarkable that if vital beings do not 

 return to life but when they have been speedily deprived of 

 the necessary caloric, this law should be general, as ani- 

 mals exposed to excessive heat do not return to life but 

 when their temperature is rapidly changed. As this may 

 be easily conceived, I shall mention only one example. 



Of four lively frogs, which appeared to be of the same 

 age, exposed in water to a heat equal to + 35°, a degree 

 fatal to these animals, only two, which were immersed sud- 

 denly at that temperature in water at 4- 16°, were recalled 

 to life. It is always, therefore, a sudden privation of caloric 

 which leaves organic beings in a state susceptible of life. 



Since our present knowledge of physiology inclines us to 

 admit an identic vital principle throughout the whole of 

 living nature, it is very probable that the general laws of 

 vitalitv are the same in all living beings, and particularly 

 in animals. For this reason, facts which relate to one only 

 of the universal agents, such as caloric, cannot fail of being 

 applicable to several other living beings. For if attention 

 be paid to the difference which there is, for example, be- 

 tween the ceconomy of the spider and that of a caterpillar, 

 one will be convinced that an agent which exercises its ac- 

 tion in a manner altogether similar on these two species of 



animals. 



