230 



NUTRITION 



warmer by 35 C. Contrast with this the conditions in mammals. Many 

 healthy persons, for example, go through life with a temperature-varia- 

 tion of less than 2 C., while we may be sure that the heat-range of the 

 average individual is not over 4, say from 36 to 40 C. (96.8 to 

 104 F.). (Unless otherwise stated, all temperatures in this book are 

 in the Celsius (centigrade) scale.) Parry and Lyon observed that the 

 temperature of an Arctic fox in a temperature of 35.6 was 38.3, while 

 Davy found the temperature of a trout in water at 4.4 to be 5.6. 

 Thus the temperature-range of the "cold-blooded " animal averages 

 nearly ten times that of the warm-blooded bird or mammal. The reasons 

 for this difference are mainly two: poikilotherms have a much less 

 active metabolism than have homotherms, and they have no elaborate 

 mechanism for maintaining a constant temperature such as is found in 

 birds and mammals. Both this katabolism and this mechanism will 

 be found described in their proper places. 



FIG. 124 



Hourly variation in the internal human temperature as given by Forel. On the left are the 

 degrees of the Celsius scale, and at the bottom the hours of the day, beginning at midnight. 

 The extreme variation is nearly 0.8 C. 



Human Temperature is of much clinical importance, because it indicates 

 better than any other one thing many conditions of illness and their 

 progress, and no other artificial instrument is so indispensable to the 

 physician as his clinical thermometer. As is the case with all biological 

 data, average temperature or mean temperature is more or less misleading, 

 for each patient is a unique individual, varying more or less from every 

 average; none the less, averages and means have use. It is customary, 

 therefore, to speak of the normal human temperature as about 37. l a 

 (98.8 F. nearly). This is a few tenths of a degree too high for men 

 and a few tenths too low for women, especially for female children. 

 In the axilla, too, it is slightly less than this, and in the rectum or vagina 

 or stream of urine nearly 1 more. Other normal causes of variation 

 act on the principle that the more intense the body's metabolism the higher 

 is the degree of heat produced. Thus, the temperature is somewhat 

 higher after meals, in the day than in the night, at sunset than at sunrise, 



