578 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



of the male. In observations on children Sommer noted a difference of 0.05 

 C., and Fehling a difference of 0.33 C. 



Individuals with vigorous constitutions have a somewhat higher temper- 

 ature than those who are weak. 



Records obtained by various European investigators indicate that the bodily 

 temperature is subjected to regular diurnal variations. The limits of variation 

 in health are from 1 to 2 C. The maximum temperature observed is usu- 

 ally from 5 to 8 P. M. (mean, about 7 P. M.) ; the minimum, from 2 to 6 A. M. 

 (mean, about 4 A. M.). Carter's l experiments on rabbits, cats, and dogs show 

 that rhythmical temperature-changes occur in these animals which agree with 

 those noted by Jiirgensen in man. This same rhythm is stated to occur during 

 fasting, so that the ingestion and the digestion of food cannot be claimed to 

 account for it ; moreover, it is present in fever and not disturbed by muscular 

 activity and by cold baths. If an individual works at night and sleeps during 

 the day, thus reversing the prevailing custom, the temperature curve is 

 reversed, the lowest temperature being noted in the evening and the highest 

 in the morning. 



Insufficient diet causes a lowering of the temperature ; a liberal diet tends 

 to cause a rise slightly above the normal mean, especially during forced feeding 

 or when the food is particularly rich in fats and carbohydrates. There is a 

 rise during digestion which is usually slight, but it may reach 0.2 or 0.3, the 

 increase being due chiefly to the activity of the intestinal muscles (see p. 540). 

 Although considerably more heat is produced during the periods of digestion 

 than during the intervals, the excess is dissipated almost as rapidly as it is 

 formed, so that but little heat is permitted to accumulate and thus cause a rise 

 of temperature. Hot drinks and solids tend to augment, and cold drinks and 

 solids to lower bodily temperature. In the nursing child Demme found that the 

 rectal temperature sinks during the first half-hour after taking food, then rises 

 during the next sixty to ninety minutes to a point from 0.2 to 0.8 C. higher 

 than the temperature before feeding, and falls again during the next thirty to 

 sixty minutes. 



All conditions which increase metabolic activity are favorable to an increase 

 of temperature. Thus, during the activity of the brain, glands, muscles, etc., 

 more heat is produced than when the tissues are at rest ; indeed, so abundant 

 is heat-production during severe muscular exercise that the temperature of the 

 body may rise as much as 0.5 to 1.5 C. (1 to 2.7 F.). During sleep the 

 temperature falls from 0.3 to 0.9 C. or more in young children. 



During the summer the mean bodily temperature is from 0.1 to 0.3 C. 

 higher than during the winter. In warm climates it is about 0.5 C. higher 

 than in cold climates, but the difference is not due to race, since it is observed 

 in individuals who have changed their habitations from one climate to another. 

 Continued exposure to excessively high or low temperatures is inimical to 

 life. Exposure in dry air at a temperature of 100 to 130 C. may cause 

 the bodily temperature to increase as much as 1 to 2 C. within a few minutes, 

 1 Journal of Nervous and Mental Diseases, 1890, vol. xvii. p. 782. 



