J5Q J. Lindhard. 



do not suffer under abrupt transitions in the light conditions, ac- 

 companied by great changes in the air-pressure, my series are much 

 more uniform than the corresponding ones for the Alps. The dif- 

 ference between the extreme points is less in my experiments than 

 in the latter, which is most probably due in the main to difference 

 in the intensity of the light; but the fact that my respiration-frequ- 

 ency is on the whole relatively low certainly also comes into con- 

 sideration. The relative reduction in my experiments is almost as 

 great as in the mountain experiments. 



The frequency in the Greenland winter and spring experiments 

 is considerably higher than in Copenhagen. According to Hassel- 

 balch's investigations cited above, the respiration-frequency is a 

 function of the state of contraction of the peripheral vessels, and 

 this would mean, therefore, contraction of the peripheral vessels in 

 the Greenland winter. This is also very probable. Direct experience 

 shows, that one can much more easily stand severe cold in the 

 winter than later in the spring, when the sun begins to make its 

 influence felt, and the organism's protection against cold is mainly 

 the contraction of the peripheral vessels. Measurement of the blood- 

 pressure in the peripheral arteries points in the same direction. 

 The average of 14 measurements of the blood-pressure in the art. 

 rad. sin. in July 07 was 148-5 mm., and of 13 measurements in Oc- 

 tober 06 156 mm. The measurements were made with Oliver's 

 gauge. But as the measurements of blood-pressure are on the whole 

 not so very accurate and self-observations especially difficult in this 

 direction, I shall not lay too great weight on these results here. 



Low temperature may however also influence the respiration- 

 frequency in another manner. Here it is not the absolute tempera- 

 ture that is considered, but the feeling of cold, perhaps, as Haldane 

 has remarked in another connection, of an effect on the respiratory 

 centre by reflexes, especially from the skin of the face and the 

 hands. The feeling of cold reduces the frequency. The decrease 

 cannot be expressed in numbers from my experiments; but the 

 result is nevertheless obvious at several places. The few experiments 

 which come in question here have already been discussed and need 

 not been repeated here. 



The air-pressure, as already mentioned, has a distinct influence 

 on the respiration-frequency in several of my experimental series. 

 To give a clearer view of my material I have represented the baro- 

 metric height and the respiration-frequency graphically on the ac- 

 companying diagram; the scale is: 1 cm. = 2 respirations = 20mm. 

 barometric pressure; the numbers at the side indicate the level of 

 the curves. 



