g2 J- Lindhard. 



did not find in the respiration experiments, but as its influence on 

 the blood and circulation was undoubted, I resolved to follow up 

 any possible effect of these meteorological factors through all the 

 series of experiments. 



The respirational functions which were to be made the object 

 of close investigation were therefore, frequency of the respiration, 

 metabolism, carbonic acid tension in the alveoli and also the total 

 amount of air respired. As I had to expect that the conditions for 

 work would be difficult, my aim was to get along with the fewest 

 possible and the least complicated apparatus. I therefore counted 

 the respiration frequency myself during the experiments, which also 

 had the advantage of giving me suitable "occupation". With regard 

 to the metabolism, the oxygen analysis was given up and only the 

 amount of CO о given off determined. I measured the expired air 

 by means of a gas-measurer and analysed both the inspired and 

 expired air. As I was unable to determine the amount of COg 

 given off for very long periods, I was obliged, in order to obtain 

 comparable data, to take care that the experiments were carried out 

 under as uniform conditions as possible; that is, I was obliged to 

 make the experiments on fasting individuals and in the most com- 

 fortable positions possible, so that the influence of the muscles 

 should be reduced to a minimum, and especially, in order that there 

 should be no appreciable difference in this regard from the one ex- 

 periment to the other. I was also obliged to take care that the 

 composition of the inspired air was to some extent constant; I had 

 to breathe directly from the outer air, as the air in the cabins often 

 contained such a large amount of CO о that it had a distinctly ap- 

 preciable effect, both on the respiration and on the cerebral func- 

 tions. This led, on the other hand, to the misfortune, that I was 

 obliged to give up the respiration experiments on days, when the 

 weather was very bad, because the "breathing pipe" could not be 

 kept open. 



As already mentioned, it was necessary to restrict the number , 

 of instruments as much as possible and I resolved therefore to 

 determine the COo-tension in the alveoli by calculation, for which 

 indeed the experiments contained the necessary data; all the more, 

 as the uncertainty arising from the "dead-space" in the calculations 

 seemed no greater than the uncertainly, which for several reasons 

 accompanies the direct determination according to the method of 

 Haldane and Priestley. 



