BODY TEMPERATURE. 951 



orated from the lungs and thus more heat is lost.* The distinc- 

 tion between the two great groups of animals is not absolute, but 

 it is sufficiently marked to constitute a striking physiological char- 

 acteristic. 



The temperature of the human body is measured usually by 

 thermometers placed in the mouth, in the axilla, or in the rectum. 

 Measurements made in this way show that in general the tempera- 

 tm-e in the interior of the body (rectal) is slightly higher than on the 

 surface of the skin. The average temperature in the rectum is 37.2° 

 C. (98.96° F.); in the axilla, 36.9° C. (98.45° F.); in the mouth, 

 36.87° C. (98.36° F.). We may speak of the body temperature, 

 therefore, in the places in which it can be conveniently measured, as 

 varying between 36.87° C. and 37.2° C. Some of the internal or- 

 gans have a higher temperature, particularly during their period of 

 greatest activity. The temperature of the skin is naturally some- 

 what lower than that of the interior. The actual temperatures 

 observed vary with that of the surrounding air, the amount of 

 movement in the air, the character of the clothing, etc., but 

 observations show that under uniform conditions the tempera- 

 tures of different parts of the skin are by no means the same. 

 Thus the body when unclothed at an outside temperature of 

 14.6° C. showed a skin temperature at the waist and chest of 30° 

 C, while at the ankle it was only 20° C. f The temperature of man, 

 measured in the places mentioned, shows also a distinct variation 

 during the day, a diurnal rhythm. This daily variation has been 

 measured by many observers, and shows individual peculiarities 

 that depend largely upon the manner of living, time of meals, etc. 

 In general it may be said that the lowest temperature is shown early 

 in the morning — 6 to 7 a. m.; that it rises slowly during the day to 

 reach its maximum in the evening, 5 to 7 p. m. ; and falls again during 

 the night. The difference between early morning and late after- 

 noon or evening may amount to a degree or more centigrade, and 

 this fact must be borne in mind by physicians when observing the 

 temperature of patients. Muscular activity and food appear to be 

 the factors that are mainly responsible for the rise in temperature 

 during the day. Most observers state that when the habits of life 

 are reversed for some time — that is, when work is performed and 

 meals are eaten during the night, and the day is given up to sleep 

 and rest, the daily variation of temperature is inverted to corre- 

 spond; the highest temperature is observed in the early morn- 

 ing and the lowest in the late afternoon. Age also has a slight 

 influence. Newborn infants and young children have a some- 



* See Langlois, "Journal de physiologie etde pathol. g6n6rale," 1902, 249. 

 t Benedict, Miles, Johnson, "Proceedings of the National Academy of 

 Sciences," 5, 218, 1919. 



