f>0 Dr. W. Marcet. The Influence of Exercise [June 8, 



Therefore, so far, the accumulation of C0 2 in the body may only 

 be considered as regular under certain fixed conditions ; but there 

 is invariably a tendency towards C0 2 being retained in the blood 

 the first few minutes exercise is taken after a period of repose. 



A certain number of minutes after exercise has been commenced 

 the C0 2 stored up in the blood is given out. In C. Bernard's ex- 

 periment, where a solution of sulphuretted hydrogen is injected 

 into the circulation of a dog, the gas comes out at the mouth in large 

 volumes in a few successive expirations following deep inspirations. 

 I should be inclined to think that a similar phenomenon takes place 

 with reference to C0 2 in respiration under exercise, the gas accumu- 

 lates in the blood up to a certain stage, and is then given out in the 

 form of a wave, after which the accumulation goes on afresh, but 

 the phenomenon is not regular, and depends on many causes which 

 would be very difficult to determine. My experiments are certainly 

 opposed to the idea that under exercise the C0 2 is eliminated as 

 fast as it is produced, leaving a uniform balance of C0 2 in the blood. 

 With prolonged exercise and training the intermittence would prob- 

 ably become Jess and less. 



One of the questions for investigation which occurred to me in the 

 course of this enquiry was the time required for the carbonic acid 

 expired and oxygen absorbed to return to their normal condition 

 of rest after the stepping exercise. This portion of work was done 

 in the season 1891-92, when Mr. Darnell Smith, B.Sc., acted as my 

 assistant. We both submitted to experiment. The first stage was 

 the determination of C0 2 expired and absorbed after resting for 

 half an hour perfectly still in the deck chair.* Then the person 

 under experiment took the stepping exercise for a quarter of an hour,, 

 and sat down, remaining quite still, for 10 mins. After that lapse 

 of time the C0 2 expired and O absorbed were again determined. 

 The results are shown in the following table (p. 51). 



It will be seen in this table that, with both of us, after 10 mins/ 

 rest the CO 2 expired had returned to the normal, or very nearly so. 

 In my case the C0 2 had quite recovered its mean in repose ; in 

 Mr. Smith's it was only by 2 per cent, in excess. The oxygen ab- 

 sorbed was, however, quite altered from its original figures. Instead 

 of 31'7 c.c. I absorbed per minute in repose, the figure had fallen 

 to 24'8 c.c., and with Mr. Smith it had been reduced from 25'8 c.c. 

 in repose to 14 c.c. The reason of this phenomenon appears to me 

 very obvious. While the respiratory phenomena are all excited under 

 exercise, the blood becomes charged with more oxygen than it can 



* In three of these experiments, on the assumption that 30 mins.' rest after 

 exercise were sufficient for a return of normal breathing in repose, the CO 2 and O 

 were determined 30 mins. after the exercise was over instead of before the exercise 

 was begun. 



