46 Dr. W. Marcet. The Influence of Exercise [June 8, 



breathing, and then the air he expired was collected as usual for a 

 period of 13 or 14 mins. In this way the whole phenomenon of 

 respiration under exercise could be closely followed. The C0 2 alone, or 

 C0 2 and O, were determined in the air expired in the state of repose, 

 the CO 2 and were determined in the air expired under exercise, 

 and the C0 2 alone in the air expired while resting after the period of 

 exercise. It had been found, experimentally, that the time taken to 

 fill the two bell-jars (13 to 14 mins.) was sufficient for the C0 2 

 expired to return to its normal amount. 



The object of the experiment was as follows : The first stage in 

 repose afforded data towards the comparison of the effects of exercise 

 on the respiratory functions with those functions in the state of rest. 

 The second stage had for its object to determine the C0 2 and O 

 expired in a given time while under the exercise. The third stage 

 showed the amount of C0 2 given out, while quite still, after the 

 exercise had been concluded ; and the excess of C0 a thus obtained 

 over the amount of C0 2 which would have been expired in the same 

 lapse of time in perfect repose was looked upon as C0 2 which had 

 accumulated in the blood during exercise, and this was proved by 

 subsequent experiment. 



[ISth August. Without entering at present into a discussion of this 

 subject, a number of experiments, which I regret space does not allow 

 me to describe, have shown most distinctly that respiration while in 

 repose following exercise cannot be compared to forced respiration, 

 inasmuch as in forced respiration the excess of C0 2 expired is much 

 less than after exercise ; and, moreover, immediately after a return to- 

 natural breathing after forced respiration the CO* expired is dimin- 

 ished nearly, although not quite, to the same amount as it had been, 

 increased under forced breathing, and this is not observed as a sequel 

 to exercise. 



I feel called upon to make this remark in due consideration to 

 C. Speck's interesting paper on the consumption of oxygen and pro- 

 duction of carbonic acid (* Schriften der Gesellschaft zur Beforderung 

 der Gesammten Naturwissenschaften zu Marburg/ vol. 10, 1871.)] 



The experiments on myself will be considered first : They were 

 undertaken in December, January, and February last, and, with two 

 exceptions, all between 1 and 2 hrs. after a full luncheon. The 

 duration of the exercise was from about 17 to 19 mins., this period 

 being selected, because after 19 or 20 mins. the phenomena were 

 found to lose their regularity. The respiratory changes were also 

 observed to be more regular in winter than in summer, and especially 

 under the direct influence of digestion ; or under circumstances pro- 

 ducing most carbonic acid in the state of repose. 



These experiments show that, in my case, under the kind of 

 exercise taken, the amount of C0 2 expired per minute was very 



