1893.] on the Interchange of the Respiratory Gases. 



51 



Time for Return of Normal Respiration after Exercise. 

 The Author under experiment. 



hold in the state of rest ; therefore under the state of repose follow- 

 ing exercise, the blood is sufficiently rich in oxygen to supply the 

 tissue-change without drawing upon atmospheric air for a further 

 amount of the gas. 



In the experiments related above, 10 mins.' rest after exercise 

 sufficed for the carbonic acid expired to return to its normal amount 

 in the state in repose ; possibly with some other persons a little longer, 

 say, 15 mins., may be necessary. As for the period of rest required 

 for the absorbed to return to its normal figure in repose, after step- 

 ping exercise, half an hour appeared perhaps barely sufficient. I 

 have considered, however, half an hour's rest as long enough when 

 active exercise had not been previously taken ; and half an hour's 

 repose was adopted, as a rule, to bring the body into the physiological 

 state of rest. 



The following is a summary of the contents of this paper : 

 1st. I have shown that in three persons out of four there was a 

 great tendency to an uniformity of figure for the oxygen consumed 

 under similar physical circumstances (food, temperature, &c.), so 

 that, if the C0 2 expired fell, the oxygen absorbed rose, and vice 

 versa ; this was accounted for by assuming that an increase of 00^ 



E 2 



