2 TEMPERATURE FLUCTUATIONS IN THE HUMAN BODY. 



somewhat high specific heat of approximately 0.83 j 1 the body of a man weighing 

 66.6 kilograms would consequently have a hydrothermal equivalent of about 

 55 kilograms of water, so that a change in its temperature of 0.1 C. would pro- 

 duce either a storage or a loss of 5.5 calories of heat. According to the standard 

 value which has been computed, the heat production of a man of this weight 

 and under these conditions would be 71 calories; consequently the amount of 

 heat absorbed or given up by the body as a result of the change in temperature 

 of 0.1 C, i. e., 5.5 calories per hour, would be approximately 7.7 per cent of 

 the total. This discrepancy is too great to permit the measurement of the 

 heat elimination to be taken as an index of the heat production. 



Practical experience has shown that a change in temperature amounting to 

 0.1 C. is very likely to occur, even with enforced body quiet and rest; as a 

 matter of fact, a normal variation in temperature amounting to 1.5 C. is 

 easily possible in a period of 24 hours. If, as is wholly unlikely, such a large 

 variation as 1.5 C. should take place in a shorter experimental period as, for 

 instance, 1 hour, there would be, under the conditions previously cited, a 

 liberation or storage of heat of 82.5 calories. If this heat were stored instead 

 of being eliminated, it is quite conceivable that during the 1-hour period 

 the body would produce heat at such a rate as to raise its temperature 1.5 C, 

 with the elimination of absolutely no heat. While such conditions are physio- 

 logically impossible in so short a period, yet when physiologists are attempt- 

 ing to measure the heat production for periods of 1 hour or less a knowledge 

 of even slight variations in body-temperature is of great importance. 



The determination of the fluctuations in body-temperature in 24-hour 

 respiration calorimeter experiments is not of particular importance, since one 

 would expect to find approximately the same body-temperature at approxi- 

 mately the same hour of the day; thus, all of the earlier experiments published 

 by Atwater and Benedict 2 were planned on the assumption that at 7 o'clock 

 in the morning, (the end of the 24-hour period) the body composition of a 

 subject existing on a uniform diet was constant from day to day, and the 

 body-temperature returned to essentially the same level at this time. When 

 the attempt is made, however, to shorten the experimental periods to 8 hours, 

 6 hours, 2 hours, or even less, an exact knowledge of the body-temperature 

 at the beginning and end of each period becomes of more and more importance. 

 By means of respiration calorimeters, 3 it is now perfectly feasible to measure 

 the chemical factors of metabolism, namely, the carbon dioxide excretion, 

 oxygen consumption, and water vaporization, in periods of 1 hour; indeed, in 

 the past few months, experimental periods of three-quarters of an hour have 

 been successfully carried out and made a part of the regular routine of this 

 laboratory. The heat eliminated can be likewise measured, and it remains 

 only to make an accurate measurement of the body-temperature to secure the 

 data for computing with considerable exactness the heat production during 

 these periods. 



'Pembrey, loc. cit., p. 839. 



*Atwater and Benedict, U. S. Dept. Agri., Office Exper. Sta., Bull. 136, 1903. 



'Benedict, Riche and Emmes, Am. Journ. Physiol., 1910, 26, p. 1. 



