78 DR SUTHERLAND SIMPSON AND DR J. J. GALBRAITH ON 



After these observations were concluded, the monkeys were used in the laboratory 

 for other purposes, and when killed within a few weeks of the conclusion of the experi- 

 ment, they were found on post-mortem examination to be healthy and free from any 

 trace of tuberculosis. 



The monkeys were tied up at 9 p.m. and let loose again at 9 a.m., when work in 

 the laboratory commenced for the day. For this reason the resting and active periods 

 were made in the first stage of the experiment from 9 to 9. It has been shown above 

 that the axillary temperature is as reliable as the rectal, and we selected the former for 

 the reason that the readings could be so much more easily obtained. In fact, during 

 the resting periods the thermometer could be slipped into the axilla almost without 

 awakening the animals, and with so little disturbance that if they did wake up they 

 were generally asleep again before the observer left the room. After a considerable 

 preliminary period, during which we took unrecorded readings in order to accustom 

 them to the hours and conditions of life and to the necessary manipulations, two- 

 hourly observations were recorded throughout the twenty-four hours. From these 

 records a curve was plotted out in each case showing the mean diurnal wave for each 

 of the periods, and a mean curve was also calculated for the whole five monkeys for 

 each period. These were found to correspond in every respect with those got during 

 our earlier observations. The actual curve for any given day only differed from the 

 mean curve in showing more irregularities, as may be seen by comparing the coloured 

 chart in the Appendix, which gives the results in three monkeys in extenso, with the 

 corresponding charts in the text (figs. 1, 2, 3, 8, 9, 10). 



Division of Experiment into Six Periods. 



These preliminary remarks suffice to show the general arrangements for the whole 

 duration of the work. The experiment was divided into six periods. In the first or 

 normal period the incidence of night and day was the natural one — the monkeys slept 

 or rested during the night and were active during the day. In the second period the 

 conditions were reversed — they slept during the day and were active during the night ; 

 and the third period was merely a modification of the second. During the fourth 

 period they were kept in total darkness, and during the fifth in continuous light. The 

 sixth period deals with the effect of alimentation on the mean temperature and its 

 range. 



Results. 



The readings are given in tabular form in the following pages for each monkey, 

 A, B, C, D, E. and F, as they were recorded, with the corresponding room temperature, 

 and the mean temperature of the whole for each hour is calculated. 



