EXCHANGE OF COLD-BLOODED ANIMALS. 



701 



ordinary conditions is so small that it may be neglected. It is to 

 be noted, however, that Colasanti and Tinkler 1 always found small 

 (quantities of marsh gas and hydrogen in the respiration chamber 

 in which well-fed guinea-pigs were placed ; these gases probably 

 came from the alimentary canal, for they were not found in the case 

 of guinea-pigs deprived of food. Zuntz 2 and Tacke found that three- 

 quarters of the hydrogen and marsh gas formed in the alimentary 

 canal of a rabbit were absorbed by the blood and discharged by the 

 lungs. 



The respiratory exchange of cold - blooded animals. When 

 compared with warm-blooded animals, the respiratory exchange of 

 most cold-blooded animals is very small, a fact which explains the 

 small production of heat observed in this class of animals. 3 Some 

 of the earliest determinations were those made by Vauquelin, 4 

 Spallanzani, 5 Newport, 6 Treviranus, 7 Edwards, 8 and Mliller. 9 They 

 showed that the quantity of oxygen consumed and of carbon dioxide 

 produced was for equal weights of animals generally much less in cold- 

 blooded than in warm - blooded animals, the most marked exception 

 being in insects. Later researches have confirmed these general conclu- 

 sions, and have shown the conditions, which chiefly affect the respiratory 

 exchange in these animals. Of these conditions the most important is 

 the external temperature, a rise in temperature causing an increase, a 

 fall in temperature a decrease in the respiratory exchange. In the 

 following table the results of various observers are expressed for 

 1 kilo, weight of animal and 1 hour, in order that they may be 

 comparable : 



l ArcJi.f. d. ges. Physiol., Bonn, 1877, Bd. xv. S. 603. 



^Arch.f. Physiol. , Leipzig, 1894, S. 354. See also this article, p. 729. 



3 Article "Animal Heat," this Text-book, vol. i. p. 792. 



4 Ann. de. chim., Paris, 1792, tome xii. p. 273. 



5 " Mem. sur la respiration," par Senebier, 1803, p. 184; Journ. f. Ckem. Physik. 

 u. Min., Berlin, Bd. iii. S. 378. 



6 Phil. Trans., London, 1837, pt. ii. p. 253. 



7 Ztschr. f. Physiol., 1832, Bd. iv. S. 23. 



8 " De 1'influence des agens physiques sur la vie," Paris, 1824. 



9 " Elements of Physiology," trans. Baly, 1838, vol. i. p. 310. 



10 Journ. Physiol., Cambridge and London, 1895-96, vol. xix. p. 18. 



