1893.] on the Interchange of the Respiratory Gases. 45 



These experiments show a remarkable uniformity of results in 

 winter and summer respectively. 



As to the experiments fasting, not tabulated in this paper, while in 

 summer they agree with those of the three other persons under 

 experiment, no uniform relation can be traced in winter between the 

 00 2 expired and O absorbed. 



In this case, in the winter and summer' experiments referred to, 

 the C0 2 expired and absorbed may be said to rise and fall 

 together, which means that, instead of a tendency to a constant figure 

 for consumed, there is, at all events between 1 and 2 hrs. after a 

 full meal, the reverse tendency, and the figure for consumed is 

 observed either to rise or fall. Consequently there must be in the 

 case of Mr. Davis a function of the body different from the corre- 

 sponding function in the three other persons. Now this gentleman 

 is just twenty-one years of age and is still 'growing ; indeed, there has 

 been a marked appearance in him of physical development within the 

 last few months, and I fully believe that this is the cause of the 

 present result. While with the three other persons as the carbonic 

 acid increased the oxygen absorbed diminished, in this particular case 

 as the C0 2 increases the absorbed also becomes larger, this excess 

 being due, it may be concluded, to the requirements of new tissue. 



Influence of Exercise. 



The method of investigation was as follows : In order to adopt a 

 kind of muscular exercise similar, as near as possible, to one in 

 common use, I selected the very simple act of stepping, within a 

 small area, which imitated walking. This was done by raising the 

 feet alternately sixty-eight times a minute, according to the striking 

 of a metronome. I raised the feet by nearly 10 cm., and Mr. Davis 

 by nearly 18 cm., measured at the heel ; consequently the degree of 

 exercise was not the same in each case. Moreover, the exercise may 

 not have 'been strictly regular in every experiment, although suffi- 

 ciently so for the purpose in view. In most cases, before exercise 

 was taken, a preliminary experiment was made on the person in 

 repose; with that object he rested for half an hour, reclining in a 

 deck chair, then the air expired in a recorded time (in absolutely 

 natural breathing) was collected in the two bell-jars, measured, and 

 then transferred to an india-rubber bag faced with oil silk, in order 

 to liberate the bell-jars for further use. The next part of the experi- 

 ment was stepping and breathing the air expired into a bell- jar 

 during exercise. It must be understood that this air was not col- 

 lected during the whole time the exercise lasted, but only at the end 

 of that time, and during about " 3 mins." 



After the air expired, under exercise, had been collected in a bell- 

 jar, the person experimented upon sat down in the deck chair without 



