INTRODUCTION. 7 



rectum. First, as has already been pointed out, the thermometer should not 

 be inserted in the fecal mass. If there is any danger of this, the fecal matter 

 should be removed by a water enema; also, sufficient time should elapse 

 between the taking of the enema and the beginning of the temperature obser- 

 vations to make sure that the change in the local temperature produced by the 

 water is not affecting the temperature of the rectum. Second, the thermometer 

 must be inserted sufficiently deep to give the maximum temperature, the depth 

 required being readily found by testing, and noting the point at which the 

 maximum temperature occurs. If the thermometer is constructed of non- 

 irritating material, there is very little liability of any local congestion. The 

 experience of observers with glass mercurial thermometers has led to some 

 difficulty in securing long-needed observations of body-temperature, owing 

 to the rigid construction of the thermometers, but with the flexible thermome- 

 ter employed by Benedict and Snell 1 continuous observations can be readily 

 made in periods of several days, the thermometer being removed only for 

 defecation. It seems well established, therefore, that with a proper construc- 

 tion of the thermometer the fear of local congestion may be entirely eliminated. 



CONSTANCY OF RECTAL-TEMPERATURE. 



If the rectal-temperature is to be used as the base-line, it is natural to assume 

 that there should also be a more or less constant temperature which should be 

 taken as the base-line, and we can properly question whether or not the rectal- 

 temperature is sufficiently constant for this purpose. Obviously the tempera- 

 tures which are markedly above the average of a large number of observations 

 may be taken as indicating fever and should not be used as a base-line. On the 

 other hand, there may be a fluctuation in the normal temperature amounting 

 to 1.5 C, and any fluctuations within this limit may be reasonably taken as 

 normal for the individual under experimentation. Before assuming that the 

 observations of the rectal-temperature represent a normal value for the indi- 

 vidual, however, we should examine carefully to find what factors affect the 

 body-temperature. 



FACTORS AFFECTING BODY-TEMPERATURE. 



Exposure to severe cold lowers the temperature, provided there is no shiver- 

 ing incidental to an attempt on the part of the body to compensate for the 

 excessive heat lost. The ingestion of hot or cold food and drink, likewise 

 muscular work, produces an almost immediate effect. In connection with 

 muscular work, it is important to note that there may be not only internal, 

 but also external muscular work; consequently, for the strictest comparison, 

 the temperature of the subject should be measured under constant condi- 

 tions of muscular activity, ingestion of food, etc. 



Furthermore, it has long been known among physiologists that there is a 

 rhythm or periodicity in the temperature of the body. By experiment, it has 



Benedict and Snell, Archiv f. d. ges. Physiol., 1901, 88, p. 492. 



