136 J- Lindhard. 



When the organism has adjusted itself to a certain temperature, 

 and such an adjustment, at any rate in arctic regions, is very readily 

 felt, fluctuations from this when they reach a certain amount will 

 be felt as more or less unpleasant. A cold day is felt all the more 

 and as more disagreeable the further we get on into the spring, 

 and conversely, in winter, a day or a period with relative high 

 temperatures will have a great effect on the state of health. How 

 far the effect of such a change in the temperature extends, will 

 depend naturally, not only on the intensity of the change, but also 

 on individual idiosyncrasies. 



It will be seen from the tables, that there is a change in the 

 carbonic acid tension in the direction indicated by Haldane, when- 

 ever the experiment was made at a lower temperature than usual. 

 The condition is most distinct in the April experiments. We find 

 here, experiment No. 31, simultaneously with a slight fall of the 

 barometer a considerable fall in the temperature and a sharp rise 

 in the tension of the alveolar carbonic acid. As already mentioned, 

 this rise is straightened out in the course of the following days, 

 irregularly owing to the simultaneous, considerable fall of the baro- 

 meter, but undoubtedly in the first place owing to an adjustment 

 to the low temperature. That this last factor is the most important 

 will appear from the values for the total volume of air respired, 

 about which more will be said below. The last experiment of the 

 series shows a well-marked fall in the air-pressure simultaneously 

 with the temperature fall, whilst on the previous day there was a 

 high carbonic acid tension with the high barometer; from this comes 

 the relatively low value for the carbonic acid tension in the last 

 experiment in spite of the fall of temperature. A distinct sign of 

 the influence of the cold is also shown in the last experiment for 

 August, experiment No. 66, as also in the three morning experiments 

 for May. The influence is here very distinct owing to the fact, that 

 the experiments do not fall on three successive days; there is no 

 "adjustment", and each of these experiments thus comes to corre- 

 spond to the first "cold day" in April. 



Haldane believes that the effect produced on the carbonic acid 

 tension is due to a reflex action on the centre from the skin of the 

 face and bandst 



This view falls in line with my experiments. Whilst the respira- 

 tory centre normally reacts to an increased carbonic acid tension 

 with increased volume of air respired, the opposite is the case on 

 my "cold days", and this can only mean that the irritability of the 



1 The Journal of Physiology. Vol. XXXVII, 1908, p. 360. 



