218 GRAVITY, LIGHT, AND CALORIC. L-ECT. XI. 



Action of Caloric on organized Beings. I have, in the 

 last place, to notice the influence which heat exercises over 

 living organized beings. 



A suitable temperature is a condition essential to life. 

 The possibility of living, is indeed comprised within cer- 

 tain limits of temperature, beyond which there are no 

 examples of the development and preservation either of 

 animals or vegetables. With respect to the general mode 

 of action of heat, it will be sufficient to say, that all the 

 physico-chemical phenomena of living bodies can be pro- 

 duced within those limits of temperature, which are also 

 the limits of vegetable and animal life. 



We now know, that the different actions of contact take 

 place only at a certain temperature, and we must not forget 

 that these actions intervene in a great number of the phe- 

 nomena of living beings ; and the little which we know of 

 these actions gives us an imperfect notion only of all the 

 uses which yet remain to be made of them. 



The fecundation and germination of plants occur at a 

 certain temperature only, and the actions of contact play 

 an important part in these mysterious phenomena. 



Independently of this general mode of action of heat on 

 living beings, we must more particularly study its influence 

 upon animals. 



From that classical work, entitled, On the Influence of 

 Physical Agents upon Life, I shall draw the most important 

 discoveries that have been made on this subject, and to 

 which I shall confine my notice. 



Edwards, when studying the life of frogs, in river water 

 at different temperatures, saw that at centig. [ = 32 

 Fahr.] these animals lived eight hours ; at a temperature 

 of + 10 [ = 50 Fahr.] they lived only six hours ; at + 

 16 centig. [ = 60-8 Fahr.] two hours ; at -f 22 centig. 

 [ = 71-6 Fahr.] from seventy to thirty-five minutes ; at 



