224 Dr. W. Marcet. History of the Interchange of 



must necessarily be attended with a falling off in the oxygen absorbed. 

 Cold would thus rob the body of a portion of its oxygen and inter- 

 fere with those functions of nutrition with which the absorbed oxygen 

 is concerned. This would explain the hibernation of animals 

 their functions are arrested because the whole of the oxygen they 

 consume in winter is used up towards the formation of carbonic acid, 

 and there is none left to carry on the phenomena of nutrition. It 

 would also account for the sleepiness or stupor well known to be 

 produced by intense cold. 



When Mr. Smith was under experiment the influence of temperature 

 on the oxygen consumed and carbonic acid produced was in the same 

 direction, though much less marked than in my case. The oxygen 

 absorbed does not, however, show the same tendency to decrease with 

 a falling temperature. This does not, I consider, invalidate the 

 result as obtained on myself, the temperature of the air being higher 

 when the experiments were made on Mr. Smith than when they were 

 undertaken on myself, and the body being under the influence of an 

 early spring season in March ; while the experiments on myself were 

 made in winter, when the laboratory at times was very cold. 



3. The influence of food on the interchange of respiratory gases, 

 although being attended with a rise in the oxygen consumed and 

 carbonic acid expired, apparently varies with reference to the oxygen 

 absorbed. Young and strong persons, requiring a full allowance 

 of food, appear to absorb more oxygen while under the influence 

 of a meal than while fasting, but late in life the oxygen absorbed 

 appears to show little or no tendency to increase after a meal. 

 According to Hanriot and Richest, the carbonic acid produced increases 

 considerably under the influence of food, while the increased absorp- 

 tion of oxygen is but slight.* . 



In conclusion, I wish to allude shortly to a result embodied in my 

 former communication, and relating to the respiration of air contain- 

 ing an increased proportion of carbonic acid. Five experiments had 

 been made three on myself and two on my assistant, Mr. Russell. 

 The proportions of C0 2 in the air inspired were respectively 2'13, 

 3-14, 4-06, 379, and 3'91 per cent. It was found that the amount of 

 carbonic acid produced in a given time was lower than when pure air 

 was breathed, and that the oxygen absorbed was greatly increased. 



The following table gives the figures obtained for the oxygen 

 absorbed : 



* 'Ann. de Chimie et de Physique,' April, 1891, 



