450 HANDBOOK OF PHYSIOLOGY, 



more trifling during infancy and early childhood. The temperature falls to 

 the extent of about .2 C. (.5 F.) from early infancy to puberty, and by 

 about the same amount from puberty to fifty or sixty years of age. In old age 

 the temperature again rises, and approaches that of infancy. 



Sex. The average temperature of the female is slightly higher than that of 

 the male. 



Period of the Day. The temperature undergoes a gradual alteration, to the 

 extent of about .54-. 8 C. (1 to 1.5 F.) in the course of the day and night; 

 the minimum being at night or in the early morning, the maximum late in the 

 afternoon. 



Exercise. Active exercise raises the temperature of the body from .54-!. 08 

 C. (1 to 2 F.). 



Climate and Season. The temperature of the human body is practically the 

 same in temperate as in tropical climates. In summer the temperature of the 

 body is a little higher than in winter ; the difference amounting to about a 

 fifth of a degree C. 



Food and Drink. The effect of a meal upon the temperature of a body is but 

 small. A very slight rise usually occurs. Cold alcoholic drinks slightly 

 depress the temperature about half a degree C. Warm alcoholic drinks, as 

 well as warm tea and coffee, raise the temperature about a third of a degree C. 



Disease. In disease the temperature of the body deviates from the normal 

 standard to a greater extent than would be anticipated from the slight effect 

 of external conditions during health. Thus, in some disease, as pneumonia 

 and typhus, it occasionally rises as high as 41-41.6 C. (106 or 107 F. ), and 

 considerably higher temperatures have been noted. In Asiatic cholera, on the 

 other hand, a thermometer placed in the mouth may sometimes rise only to 

 25-26.2 C. (77 or 79 F.). 



The temperature maintained by Mammalia in an active state of life, accord- 

 ing to the tables of Tiedemann and Rudolphi, averages 38.3 C. (101 F.). 

 The extremes recorded by them were 34.6 C. (96 F.) and 41 C. (106 F.), the 

 former in the narwhal, the latter in a bat (Vespertilio pipistrella) . In Birds, 

 the average is as high as 41.2 C. (107 F.) ; the highest temperature, 46.2 C. 

 (111.25 F. ) being in the small species, the linnets, etc. Among Reptiles, while 

 the medium they were in was 23. 9 C. (75 F. ) their average temperature was 

 31.2 C. (82.5 F.). As a general rule, their temperature, though it falls with 

 that of the surrounding medium, is, in temperate media, two or more degrees 

 higher ; and though it rises also with that of the medium, yet at very high 

 degrees it ceases to do so, and remains even lower than that of the medium. 

 Fish and invertebrata present, as a general rule, the same temperature as the 

 medium in which they live, whether that be high or low ; only among fish, the 

 tunny tribe, with strong hearts and red meat-like muscles, and more blood 

 than the average of fish have, are generally 3. 8 C. (7 F. ) warmer than the 

 water around them. 



The difference, therefore, between what are commonly called the warm and 

 the cold-blooded animals, or homoiothermal (b/j.oioc, like, OepfJ-y, heat) and poikilo- 

 thermal (TTOIKI^, changeful, Oeppr?, heat) , is not one of absolutely higher or lower 

 temperature ; for the animals which to us in a temperate climate feel cold (be- ; 

 ing like the air or water, colder than the surface of our bodies) , would in an 

 external temperature of 37.8 C. (100 F.) have nearly the same temperature 

 and feel hot to us. The real difference is that warm-blooded animals have a 

 certain permanent heat in all atmospheres, while the temperature of cold- 

 blooded animals is variable with every atmosphere. 



