Contribution to the Pliysiology of Respiration under the Arctic Climate. 97 



tion, and should thus give the minimum and maximum respectively 

 for the percentage of carbonic acid. They take the average of these 

 two values, and it is this factor they regard as constant for the 

 individual. 



It seems to me that the reasoning of Haldane and Priestley 

 is unsound, or rather perhaps, that it cannot be made to agree with 

 the practice recommended by them. 



If we maintain, as Haldane and Priestley occasionally point 

 out, that the production of carbonic acid proceeds continuously in 

 the pulmonar}' alveoli, as also that the inspiration is not even 

 throughout but from a fairly sudden and energetic beginning ebbs 

 gradually before the expiration begins, as the Pneumographie curves 

 show, though the condition is less distinct than in the other phase, 

 then the minimum of carbonic acid should be found immediately 

 before the termination of the inspiration. And Haldane and 

 Priestley take their samples after the inspiration; certainly imme- 

 diately after and with rapid expiration; but, in the first place, there 

 must be time to open the mouth over the mouth-piece, and in the 

 second, it is not possible to expire through such a momentary point 

 of time, especially when the expiration has to be made more than 

 usually deep. Haldane and Priestley's own results show this. As 

 Hasselbalch^ has already remarked, their inspirational percentage 

 of carbonic acid is in several cases higher than the expirational; 

 and this appears even more strikingly in a later paper of Haldane 

 and Fitzgerald^, in which experiments are made on quite untrained 

 individuals. Here there can only be talk of experimental errors; 

 that is, to make sure that their "dead space" was completely emptied, 

 Haldane and Priestley rightly made their expirations very deep 

 and have therefore taken too long a time over them. I cannot help 

 thinking, that Haldane and Priestley's inspiration-sample should 

 come to agree to some extent with the value calculated from Bohr's 

 formula, when the expiration is made so great that one is certain 

 that the "dead space" has been emptied. Some difference may well 

 arise with regard to the rapidity of the expiration; Haldane and 

 Priestley have made experiments here, to show, that the percen- 

 tage of carbonic acid may become constant, when the expiration 

 has reached a certain stage; but by the side of so many disappoin- 

 ting samples which they show, these samples are very little con- 

 vincing. 



With regard to the second sample taken by Haldane and 



1 I.e. p. 33. 



- Tlie Journal of Physiology. Vol. 32. 



