1902.] Influence of Oxygen on the Respiratory Exchange. 461 



Consideration of Results. 



It will be noticed that the most constant results are those of the 

 carbonic acid. If the amount of this expired per minute and per 

 kilo, body weight for the different periods be examined, it will be 

 seen that there is a very distinct diminution in the amount during respira- 

 tion in a pure atmosphere of oxygen. This diminution does not occur 

 immediately, but is generally quite distinct in about 30 minutes. 



In taking an average of the amount of this gas for any period, 

 therefore, we have included the first period of the respiration in air 

 which followed it. 



The average of carbonic acid per minute and per kilo, body weight 

 for a period (varying from 1 to 3 hours) in air, is as follows : — 



]S"o. of experiment. Weight of mouse.* C0. 2 exhaled. 



1 19 -4 grammes • 1331 gramme. 



2 13-8 „ 0-1417 



3 19-1 „ 0-1074 



The low result in No. 3 is explained by the fact that the estimation 

 was made after the animal had been for over 2 hours in an atmosphere 

 of oxygen, that it had received no food during this period, and that 

 all through the metabolism in this animal was on a lower plane than 

 in the others. 



It will further be noticed that the mouse in Experiment 2 had a 

 higher average than that in No. 1, the difference , in this case being 

 due to the fact that the animal weighed less.f 



The average for a period in oxygen is as follows : — 



No. of experiment. "Weight of mouse. C0 2 exhaled. 



1 19-4 0-0831 



2 13-8 0-1187 



3 19-1 0-0993 



From this it will be seen that in No. 1 there was a diminution 

 amounting to nearly 40 per cent., in No. 2 to nearly 20 per cent., 

 -and in No. 3 to nearly 8 per cent. As it might well be argued that 

 the diminution was not due to the effect of the oxygen, but to the 

 fact that the animal was receiving no food, and was kept in a confined 

 space, we must consider the effect of an atmosphere of air following that 

 of oxygen. In the case of Experiments 1 and 2 a very distinct increase 

 (viz., 20 per cent, in No. 1 and 12 per cent, in No. 2) occurred when 

 the atmosphere was again changed to air. This increase is not 

 marked till about 2 hours after the commencement of the period. In 

 Experiment 3, the increase on changing from oxygen to air is about 



* Weighed at beginning of experiment. 



f See Schafer's " Text-book of Physiology " (1898), vol. 1, p. 720. 



