42 J- Lindhard. 



reversal of day and night is impossible; but in his opinion he has 

 come as near to it as can be done. He is hardly right here. His 

 night-watch slept unusually long and at an unusual time, while 

 eating no regular meal from 515 p.m. to 715 a.m> It might have 

 been possible, however, to find a more reasonable arrangement, 

 though the results would hardly have been changed. The difficulty 

 is the same everywhere. One cannot disconnect the individual from 

 society; so long as the latter follows a fixed rotation, the single 

 individual will, consciously or unconsciously, tend towards the same 

 mode of life. And, as Tigerstedt points out, it will always be 

 necessary, at any rate during a "reversed" day and night, to work 

 by lamp-light, sleep in the day-time, work in the stillness of night, 

 sleep through noise and so forth. 



Galbraith and Simpson^ have investigated the variations of 

 temperature in monkeys. Six monkeys were kept in a large room 

 which could be made dark in the day-time. The temperature of 

 the animals was measured every second hour in the axilla. The 

 temperature in the room was always pretty high, 19° — 23° C; 5 ex- 

 perimental series were made. 



During the 1st period, light day and dark night, a regular curve 

 was obtained with higher temperature in the day, lower in the night.- 



During the 2nd period, darkness during the day, the curve be- 

 comes reversed already after 24 hours and by and by pretty regular, 

 though not so regular as during the 1st period, according to the 

 authors, because noise in the adjacent laboratory disturbed the 

 animals. The average of the curve is a little lower than during the 

 first period. 



In the 3rd period, darkness from 3 a.m. till 3 p.m., light during 

 the remaining 12 hours, the curve follows the new division of day 

 and night, but is less regular. 



In the 4th period, darkness day and night, and in the 5th 

 period, light, electric light or day-light, day and nighl, the curves 

 become irregular, in the first case with the average a little lower. 



Thus, it is evident that the reversed curve can be produced. 

 The whole monkey society is "reversed". The world of the monkeys 

 is in the cage, and in the cage light and darkness and meal-times 

 can be arranged at pleasure. 



Galbraith and Simpson^ have also examined the curve of 

 temperature in night and day birds. They found the curve "re- 

 versed" in night birds (owls), the maximum occurring in the night 



1 Proceedings of the Physiological Society, July 1903. The Journal of Physiology, 

 XXX, 1903. 



2 1. с and The Journal of Physiology, Vol. XXXIII, 1905—06. 



