VARIATIONS OP THE MEAN TEMPERATURE, 439 



they become cold sooner, and hence ought to wear warm clothing to 

 keep up their temperature. 



(4.) Periodical Daily Variations. In the course of 24 hours there 

 are regular periodic variations in the mean temperature, and these 

 occur at all ages. As a general rule, the temperature continues to rise 

 during the day (maximum at 5-8 p.m.), while it continues to fall during 

 the night (minimum 2-6 a.m.). The mean temperature occurs at the 

 third hour after breakfast (Lichtenfels and Frohlich). 



According to Lichtenfels and Frohlich, the morning temperature rises 4-6 

 hours after breakfast until its first maximum, then it falls until dinner time ; and 

 it rises again within two hours, to a second maximum, falls again towards evening, 

 while supper does not appear to cause any obvious increase. The daily variation 

 of the temperature is given in Fig. 170, according to Liebermeister and Jiirgensen. 

 According to Bonnal, the minimum occurs between 12-3 a.m. (in winter 36*05, 

 in summer 36'45C.)> the maximum between 2-4 p.m. 



Morning. Mid-day. Evening. Night. Morning. 



Fig. 170. 



Variations of the daily temperature in health during 24 hours L , after 



Liebermeister; J , after Jiirgensen. 



As the variations occur when a person is starved although those that occur at 

 the periods at which food ought to have been taken are less it is obvious that 

 the variations are not due entirely to the taking of food. 



The daily variation in the frequency of the pulse (p. 142) often coincides with 

 variation of the temperature. Barensprung found that the mid-day temperature- 

 maximum slightly preceded the pulse-maximum. 



If we sleep during the day, and do all our daily duties during 

 the night, the above described typical course of the temperature is 

 inverted (Krieger). With regard to the effect of activity or rest, it 

 appears that the activity of the muscles during the day, tends to 

 increase the mean temperature slightly, while at night, the mean 

 temperature is less than in the case of a person at rest (Liebermeister). 



