des Agens Physiques sur la Vie. 301 



fed, and in the lively season of advanced spring. The depri- 

 vation of food seems to be a local consequence provided 

 for by the phenomenon of hybernation, and not its exciting 

 cause. Nor does there appear to be any change of organiza- 

 tion in these cases, but a state of constitution exists which 

 we are unable to account for further. 



We have, in the next place, a series of experiments showing 

 tjie influence of the seasons upon animal temperature with 

 the warm-blooded ; by which it seems that they produce a 

 variety of results : and it is demonstrated that animals of 

 warm blood in general undergo some constitutional changes 

 with the periodical returns of the seasons. When, for ex- 

 ample, the highest degree of temperature is attained, animals 

 no longer produce heat ; so that their temperature continues 

 below that of the air in the hot season. And, in the cold 

 season, if the cold be not too rigorous, the animal's age offers 

 a proportionate resistance to the cooling effects of the air 

 as the approach to maturity is attained. An elevated and 

 a depressed temperature thus produce contrary eff'ects upon 

 the internal powers of generating animal heat, a high tem- 

 perature arresting them, and a low one promoting them. 

 Thus we cannot fail to observe the beautiful adaptation of 

 means to final causes. 



Upon the subject of asphyxia in warm-blooded animals. 

 Dr. Edwards found a great dependence between animal heat 

 and the faculty of living without contact with the air, a state 

 in which the blood is not aerated by respiration, and which 

 is sustained by hybernants while in the dormant condition. 

 Having submersed animals in water of various temperatures 

 successively, so as to bring them under the influence of vari- 

 able temperature, he found the descending scale of tempera- 

 ture the most hurtful. The ascending Jieat was that which 

 prolonged life most. Between 20"^ and 10° the results were 

 similar to those between 20° and 40^ 



Animals, then, of warm blood in a state of asphyxia hold 

 their existence on two principal conditions relative to heat; 

 one regarding the different measures by which some deve- 

 lope their heat, and the other the degree of external tempe- 

 rature. The first is proper to animals naturally, the second 

 fortuitous. . 



Upon the respiration of both young and adult animals the 

 author arrives at a conclusion opposite to that of common 

 opinion, which is founded on the notion of the heat in young 

 animals being higher than that of the matured. Finding, 



OCT.— DEC* 1827. X 



