620 



FUNCTIONS OF ANIMALS. 



to believe that the oxygen absorbed by the blood in the lungs is 

 the cause why it acts as a stimulus to the heart, and makes it to 

 contract. For the action of the heart, and consequently the cir- 

 culation of the blood, immediately ceases when respiration is pre- 

 vented. This is doubtless the reason why respiration is so essen- 

 tial to life, that when it is suspended for even a very short time, 

 death ensues. 



A great number of experiments have been made on the respi- 

 ration of fishes by Prove^al and Humboldt.* It is well known 

 that these animals require oxygen gas as well as other animals, 

 and that if the water in which they are be deprived of the whole 

 of its air, they die very speedily. Prove^al and Humboldt em- 

 ployed for their experiments the waters of the Seine. They se- 

 parated the air from a quantity of it by boiling, and subjected it 

 to a chemical analysis. Into another quantity of the same water, 

 tenches were put and confined for several hours till they began 

 to suffer ; they were then withdrawn, and the air separated from 

 the water in which they had lived, and subjected to chemical ana- 

 lysis. In every case a portion, both of oxygen and azote had 

 disappeared, and a quantity of carbonic acid had been formed. 

 The following table exhibits the results of a variety of their ex- 

 periments : 



Mem- d'Arcueil, ii. 259. 

 3 



