No. 582] SIGNIFICANCE OF INTERNAL CONDITIONS 329 



The monotremes occupy a peculiar position in the scale 

 ( Table III ) . Their internal temperature, while relatively 

 constant and considerably above that of the external air, is 

 notably lower than that of mammals generally. 10 This 

 group probably presents a transition stage between the 

 poikilothermal animals and the homoiothermal animals 

 with a higher body temperature. 



TABLE IIT 



Ornithorh'ynchu* panulo.rux. '. . h'.2 2.5.2 23.0 



The normal diurnal variation in temperature of the 

 human lias been studied by many observers. The temper- 

 ature varies not only with the time of day, but with the 

 taking of food, with age, with external temperature and 

 with other conditions to which we will return later. On 

 the average, the highest temperature is attained in the 

 evening between five and eight o'clock, and the lowest in 

 the early morning between two and six, with upper and 

 lower limits of 37.5° C. (99.5° F.) and 36.3° C. (97.4° P.), 

 respectively. The body temperature may, of course, be 

 greater or less without any necessary implication of dis- 

 ease processes, but the figures given may be considered as 

 fairly representative. 17 It seems well established that, in 

 conditions of health, the daily variation in temperature 

 is about one per cent, of the mean— 98.4° F — expressed in 

 the Fahrenheit scale. It is a peculiar fact also that the 



"Richet, p. 90, Table IT, and C. J. Martin, PMosophicai Transactions of 

 tht Royal Society, London, 1903, Series B, Vol. CXCV, p. 1. 



