1891.] 



Phenomena of Human Respiration. 



Ill 



C0 2 before re-breathing calculated on time after re-breathing. 



Litres of Air expired before re-breathing calculated on time after 

 re-breathing. 



W. Alderwood, who was the least affected of the four persons under 

 experiment, the excess of C0 2 after re-breathing, amounting to 1 

 to 1'097, is the smallest. A similar remark applies to the volumes 

 of air expired ; they are invariably increased after re-breathing, or 

 while the person under experiment is still under the influence of the 

 want of air ; the mean relation is 1 to 1'307 ; again, in the case of 

 W. Alderwood the increase is the smallest, the proportion amounting 

 to 1 to 1-177. 



The excess of C0 2 and of air expired when fresh air is breathed 

 immediately after the re-breathing stage of the experiment must be 

 due in a great measure to the increased amount of carbonic acid 

 retained in the blood, together with an instinctive desire of taking 

 into the lungs increased volumes of air, in order to rid the blood of 

 the carbonic acid it has retained. 



We now have to deal with the air expired finally or in the bell-jar 

 filled at the termination of the experiment. The mean volumes of 

 air and weights of C0 2 expired per minute will be seen to approxi- 

 mate to the corresponding volumes and weights expired in ordinary 

 breathing to such an extent that respiration may be considered as 

 having returned to the normal condition. 



