INFLUENCE OF TEMPERATURE. 345 



a depression of the surrounding temperature would constantly 

 produce this effect in all classes of animals. The numerous and 

 variously modified experiments which have since been made in 

 connection with this inquiry have, however, proved that in the 

 higher classes of animals at all events there is a diminution in 

 the exhalation of carbonic acid corresponding with the rise of the 

 temperature from the freezing point. Letellier* was one of the 

 first of several observers who in recent times have made a series of 

 determinations of the quantities of carbonic acid exhaled by 

 different animals, as green-finches, turtle-doves, mice, and guinea- 

 pigs, at various lower or higher temperatures. His results showed 

 that the largest relative amount of carbonic acid was exhaled in a 

 temperature between 5 and + 3, and the smallest at a tempera- 

 ture between + 2S and 43. This ratio is more strongly marked in 

 birds than in the mammals ; the animals on which these experi- 

 ments were made were unable to bear a temperature exceed- 

 ing + 43. Almost simultaneously with Letellier, Marchand 

 obtained similar results with frogs ; with this difference only, that 

 these animals already fell into a torpid state between + 2 and 3, 

 in which they excreted a remarkably small amount of carbonic 

 acid, 1000 grammes 5 weight of frogs yielding only 0*039 of a 

 gramme in one hour, whilst the largest amount was exhaled 

 between 6 and 7> 1000 grammes' weight yielding 0*124 of a 

 gramme; the quantity of excreted carbonic acid then gradually 

 sunk in proportion to the rise of the temperature. Between 28 

 and 30, 1000 grammes' weight of frogs exhaled only 0'077 of a 

 gramme in one hour. 



Vierordt has calculated a scale of the values of the respiratory 

 functions, according to each degree of temperature between 3 and 

 24, basing his numbers on the results of his numerous experi- 

 ments on the excretion of carbonic acid, in which he noted the 

 thermometric and barometric readings, as well as the pulsations 

 arid respirations, and the volumes of the individual expirations 

 throughout the entire experiment. These tables afford a better 

 insight into the influence of the temperature on the respiration 

 than we obtain from any of the earlier observations on the same 

 subject. For the better comprehension of these relations, we 

 divide the mean result into two sections, of which the one 

 represents the means of the values obtained in the lower degrees 

 of temperature between + 3 and 13, and the other those between 

 14 and 24. 



* Corapt. rend. T. 20, p. 794. 



