Pulmonary Gases in the Respiration of Man. 223 



In Mr. Smith's case there are actually seven pairs of experiments 

 (fourteen altogether) made under the influence of food. Each ex- 

 periment was repeated at the time, and the means of the pairs were 

 taken and recorded. 



Grouping these pairs of experiments two-by-two, as shown in this 

 last table, the volumes of oxygen consumed will be found to exhibit 

 a slight decrease as the temperatures rise, the carbonic acid pro- 

 duced also shows a slight tendency to fall with the increase of tem- 

 perature. The oxygen absorbed, which in my case is unmistakably 

 increased with a rise in temperature, is not found to undergo a similar 

 change, but remains nearly the same throughout ; there being a slight 

 fall at the two highest temperatures. 



With reference to the influence of food on the interchange of the 

 pulmonary gases, the experiments made on Mr. Smith fasting, or 

 when a desire for food was felt about five hours after breakfast, 

 showed a considerable falling off in the oxygen consumed, carbonic 

 acid produced, and oxygen absorbed. Corresponding experiments 

 have been reported in my former paper. Mr. Russell, who assisted me 

 at the time, a young gentleman twenty-one years of age, also exhi- 

 bited a decrease, though but slight, of oxygen absorbed while fasting, 

 the figures being 33'3 c.c. while fasting, and 37*5 at a mean period of 

 2 hrs. 16 min. after a full meal. In my case the figures were 35'3 c.c. 

 while fasting and 30'2 under food, which show a slight influence in 

 the opposite direction. It appears, therefore, that the influence of 

 food upon the absorption of oxygen varies with different persons, 

 but that in young and strong people the absorption of oxygen has a 

 decided tendency to increase after a meal. 



The results obtained from the present inquiry may be summarised 

 as follows : 



1. Nitrogen acts a part inappreciable, if concerned at all, in the 

 interchange of pulmonary gases. 



2. The influence of changes of the atmospheric temperature on the 

 oxygen consumed, carbonic acid produced, and oxygen absorbed, al- 

 though in the present experiments this influence is more or less inter- 

 fered with by the phenomena of digestion, is distinct in my case ; the 

 oxygen consumed and carbonic acid produced increasing with falling 

 temperatures, while the oxygen absorbed is lessened ; and a similar 

 result is obtained from the consideration of the figures given in my 

 former communication. This fact is interesting, perhaps, mainly as 

 showing that the oxygen absorbed is not concerned in the formation 

 of heat in the body towards resisting cold a function which appears 

 to be limited entirely to the oxidation of carbon into carbonic acid. 

 If, as usually admitted, the blood is limited in its power of taking up 

 oxygen, although this power may apparently vary according to tempe- 

 ratures, then it is obvious that an increased formation of carbonic acid 



VOL. LII. Q 



