43 



hybernating mammals, and by minutes for birds and non-hyber- 

 nating mammals. 



III. After the removal of the medulla oblongata, the most 

 remarkable differences in the duration of life, in different indi- 

 viduals belonging to the same species, may occur in consequence 

 of differences of temperature. The lower the temperature the 

 longer is the duration of life. Thus, the duration of life in 

 frogs may be reckoned by months when the temperature is be- 

 tween 32 and 46 F., (0 and 8 Cs.) ; by weeks when it is 

 between 40 and 55 F. (5 and 13 Cs.) ; by days when it is 

 between 50 and 65^> F. (10 and 18 Cs. ) by hours when it is 

 between 65 and 72 F. (18 and 24* Cs.) ; and by minutes when 

 it is between 86 and 105^ F. (30 and 40 Cs.) 



In the other cold-blooded vertebrata the differences in the 

 duration of life, after the removal of the medulla oblongata, are 

 not so great as in frogs, but the law is the same. This law 

 exists also for warm-blooded animals, so much so that the differ- 

 ences existing between mammals of different ages and of differ- 

 ent species, are to be attributed, in part, to their differences of 

 temperature. 



IV. As the principal condition for a long duration of life 

 in cold-blooded vertebrata is a cold atmosphere, and as the 

 vital phenomena taking place in these animals are much dimi- 

 nished when they are exposed to a low temperature, some phy- 

 siologists have supposed that the persistence of life for many 

 weeks or more, was equivalent, as regards the sum of the vital 

 phenomena, to a duration of some hours in summer, when these 

 phenomena have a great activity. 



In answer to this objection I will at first call the reader's 

 attention to the fact that, in batrachia, deprived of the medulla 

 oblongata, and exposed to the action of a low temperature, the 

 heart beating, on an average, 35 times in a minute and life 

 lasting four months i. e. 172,800 minutes, it follows that, during 

 that time, the heart has more than 6,000,000 pulsations. In 

 summer, the maximum duration of life having been six hours 

 i. e. 360 minutes, and the heart beating, on an average, 45 times 

 in a minute, it results that, during that life, the heart has only 

 1,600 pulsations a number which is to the other as 1 is to 375. 



