52 On the Interchange of the Respiratory Gases. [June 8, 



in the blood in the state of repose is produced at the expense of the 

 O absorbed. The fourth person experimented upon exhibited no 

 such tendency, the C0 2 expired and O absorbed rose and fell 

 together, which was ascribed to the fact that he was still growing. 



2nd. Experiments were made on the influence of exercise on 

 respiration which showed that if stepping exercise is taken after a 

 period of rest, there occurs for a few minutes an accumulation of 

 C0 2 in the blood ; of course the degree of this storage of C0 2 must 

 be controlled by the normal amount of CO 2 produced in repose, and 

 the kind of exercise taken ; this storage would in the cold winter 

 weather, and between 1 and 2 hrs. after food continue for about 18 

 or 20 mins. In my case the volume of C0 2 retained in the blood 

 amounted to a mean of 500 c.c. while stepping sixty-eight times per 

 minute about 10 cm. high. The C0 2 in store is next given out in 

 the form of a wave, which is renewed after a certain lapse of time, 

 so that there does not appear to be in respiration under exercise a 

 fixed relation between the C0 2 expired and the C0 2 left in the blood. 

 With practice and training this relation would probably become 

 more and more uniform. 



The storage of C0 2 in winter and after food was found to exhibit a 

 certain relation to the excess of C0 2 expired under exercise over the 

 C0 2 expired in repose ; but 18 or 20 mins. after exercise had been 

 commenced this relation failed to show itself any longer. 



The ratio in question was the same with two different persons ; 

 but further experiment is required to determine whether it can be 

 looked upon as general ; the mean ratio found is shown by the figure 

 0'123 ; therefore, so far as the present enquiry goes, and under the 

 conditions expressed in this paper, by multiplying this figure 0*123 

 by the excess of C0 2 given out per minute under exercise over the 

 C0 2 expired in repose during the same lapse of time, the result will 

 show the volume of C0 2 absorbed in the blood per minute. 



After the exercise had lasted 18 to 20 mins., the volume of C0 2 

 stored up in the blood after exercise was found to vary. 



3rd. After the exercise adopted in this enquiry had been followed 

 by a complete repose of 10 mins., the C0 2 expired had returned to 

 the normal in repose, but the volume of O absorbed per minute had 

 considerably fallen, clearly owing to the blood having charged itself 

 with oxygen during exercise, so that the first few minutes after rest 

 was taken the blood was in a condition to supply oxygen for tissue- 

 changes without taking it from the air breathed. After half an 

 hour's perfect rest following exercise the respiratory changes had 

 returned to their normal state of repose, or nearly so, the oxygen 

 absorbed still occasionally showing signs of being a little lower than 

 before exercise had been taken. 



