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



clay rest produced an inversion of the temperature curve. Tims, all these observers 

 came to the same conclusion, viz. — that by inverting the daily routine the temperature 

 curve may be inverted, but in many cases the details are wanting, and where they are 

 given the conditions are often open to criticism. 



In 1885 U. Mosso (7) made an experiment on himself. He first obtained his 

 normal curve by taking the rectal temperature for several days consecutively under his 

 usual daily routine. He slept from 11 p.m. till 6 a.m. Two meals were taken, one at 

 1 1 a.m., the other at 6 p.m. During the second period, which lasted four days, he worked 

 during the night and rested during the day, sleeping from 11 a.m. till 6 p.m., and he 

 now took his meals at 11 p.m. and 6 a.m. Throughout almost the whole experiment he 

 remained in one room, the temperature of which only varied between 12° and 17° C, 

 and the greater part of his working time was spent seated at a table either reading or 

 writing ; he did no active muscular work. Notwithstanding this inversion of the daily 

 routine the morning rise still took place at about the same time, and the normal curve 

 was considerably modified by the fact that sleep during the day produced a marked 

 fall, but it was not inverted. 



The most recent and by far the most accurate research on this subject is that of 

 Benedict (6), carried out in America (1903). For the details the reader is referred to 

 the original paper. Suffice it to say that he did not find the temperature curve to be 

 inverted even in an individual who had been a night watchman for a period of eight 

 years, during the whole of which time he had slept during the day and been active 

 during the night. The curve was approximated more or less closely to a straight line, 

 but it was not inverted. From these experiments of Mosso and Benedict, then, which 

 were conducted far more systematically than those of the earlier observers, we may take 

 it that in man inversion of the daily routine produces a modification of the temperature 

 curve, but does not lead to its total inversion. 



So far as we know, ours is the first attempt to study this subject in animals. We 

 have already stated our reasons for selecting the monkey, viz. — the susceptibility of its 

 temperature to the outside influences which are supposed to be the cause of the diurnal 

 variation. Unlike Mosso and Benedict in the human subject, we have succeeded in 

 inverting the temperature curve in the monkey. The range, it is true, is somewhat 

 more variable than under normal conditions, but the inversion is nevertheless 

 complete. Still there is a certain amount of fixity in the normal variation curve, 

 although this is not nearly so pronounced as it is in man. This is evident from the 

 fact that when the monkeys were left to themselves during Periods IV. and V. 

 (continuous darkness and continuous light), without any signal from without as to what 

 routine they should adopt, the curve returned to the normal type (figs. 8-13, pp. 91-93). 

 Temperature control is therefore much more complete in man than in the monkey, as 

 is shown by the greater range in the latter and the readiness with which its normal 

 wave may be disturbed. The two chief factors which govern the diurnal variation are 

 probably muscular exercise and sleep, i.e. the condition of the great heat-producing 





