8 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY. 



been found that this rhythm is somewhat as follows : The minimum tempera- 

 ture occurs during the early morning hours, usually between 2 and 5 o'clock; 

 there is then a marked early morning rise which becomes less pronounced as 

 the day progresses, but reaches its maximum in the afternoon about 5 o'clock; 

 this is followed by a slight fall, which becomes very noticeable after retiring 

 and gradually continues until the minimum point is again reached in the 

 early morning. 



A number of attempts have been made to explain this rhythm, which as yet 

 have been only partially successful, although the rhythm appears to be more 

 or less coincident with the muscular activity incidental to the day's work. 

 This explanation is not scientifically complete, however, for it does not explain 

 why a night watchman, 1 who for seven years had been working during the 

 night and sleeping in the daytime, should still have the highest body-tempera- 

 ture at 4 or 5 o'clock in the afternoon when he was sound asleep, and the 

 lowest value at 4 or 5 o'clock in the morning when he was awake and on his 

 rounds. Daylight and cosmic influences have also been thought to have an 

 effect upon this rhythm. It is not the object of this report, however, to enter 

 into a discussion of the cause of the normal periodicity or rhythm, but in 

 any study of body-temperature this factor should be taken into consideration 

 when endeavoring to establish a base-line. For the particular reason for which 

 this investigation was undertaken, namely, to study simultaneously the tem- 

 perature fluctuations in different parts of the body in order to find whether or 

 not they paralleled each other, the absolute temperature values at any given 

 point are not of such great importance as are the variations. Consequently 

 we may assume that previous experiments have demonstrated clearly the 

 existence of a rhythm and have likewise demonstrated the difficulty of giving 

 a satisfactory explanation which covers all observations thus far made. 



Johansson's belief 2 that the body-temperature is influenced in large part by 

 the metabolism is strongly substantiated by his observations, and yet it is 

 difficult to conceive that the night watchman previously referred to had a 

 higher metabolism during the periods when he was sound asleep than when he 

 was sitting up in a chair engaged in conversation. From the well-known 

 relationship between the pulse-rate and the metabolism, it is clear that all 

 future experiments on body-temperature should be accompanied by a simul- 

 taneous observation of the pulse-rate and, so far as possible, of the metabolism 

 and its changes. In the majority of experiments, observations of the metab- 

 olism will be impossible, but records of the pulse-rate may be easily obtained 

 by practically all observers. If to these observations can be added others with 

 regard to the blood pressure and pulse pressure, the results will be still more 

 valuable, especially in throwing light upon the contention of Johansson that 

 the body-temperature is a function of the total metabolism. 



'Benedict, Am. Journ. Physiol., 1904, 11, p. 145. 



2 Johansson, Skand. Archiv f. Physiol., 1896, 7, p. 123. 



