448 NUTRITION ANIMAL HEAT AND FORCE. 



Breschet and Becquerel, who were among the first to employ thermo-electric 

 apparatus in the study of animal heat, it was found that the cellular tissue 

 was 2-5 to 3-3 Fahr. (1-37 to 1-8 C.) cooler than the muscles. As regards 

 the temperature of the blood in the two sides of the heart, experiments upon 

 the lower animals have been somewhat contradictory ; but there is no positive 

 evidence of any considerable change in the temperature of the blood in pass- 

 ing through the lungs in the human subject. In the lower animals, there 

 probably exist no constant differences in temperature in the two sides of the 

 heart. When the loss of heat by the general surface is active, as in animals 

 with a slight covering of hair, the blood generally is cooler in the right cavi- 

 ties ; but in animals with a thick covering, that probably lose considerable 

 heat by the pulmonary surface, the blood is cooler in the left side of the 

 heart. 



Variations at Different Periods of Life. The most important variations 

 in the temperature of the body at different periods of life are observed in in- 

 fants just after birth. The body of the infant and of young mammalia 

 removed from the mother presents a diminution in temperature of 1 to 

 4 Fahr. (0-55 to 2-2 C.). In infancy the ability to resist cold is less than 

 in later years; but after a few days the temperature of the child nearly 

 reaches the standard in the adult, and the variations produced by external 

 conditions are not so great. 



W. F. Edwards found that in certain animals, particularly dogs and cats, 

 that are born with the eyes closed and in which the foramen ovale remains 

 open for a few days, the temperature rapidly diminished when they were re- 

 moved from the body of the mother, and that they then become reduced to a 

 condition approximating that of cold-blooded animals ; but after about fifteen 

 days, this change in temperature could not be effected. In dogs just born, 

 the temperature fell, after three or four hours' separation from the mother, 

 to a point but a few degrees above that of the surrounding atmosphere. The 

 views advanced by Edwards are illustrated in instances of premature birth, 

 when the animal heat is much more variable than in infants at term, and in 

 cases of persistence of the foramen ovale. 



In adult life there does not appear to be any marked and constant varia- 

 tion in the normal temperature ; but in old age, while the actual temperature 

 of the body is not notably reduced, the power of resisting refrigerating in- 

 fluences is diminished very considerably. There are no observations showing 

 any constant differences in the temperature of the body in the sexes ; and it 

 may be assumed that in the female the animal heat is modified by the same 

 influences and in the same way as in the male. 



Variations in the Heat of the Body at different Times of the Day etc. 

 Although the limits of variation in the animal temperature are not very wide, 

 certain fluctuations are observed, depending upon muscular repose o,r activity, 

 digestion, sleep etc. It has been ascertained that there are two well marked 

 periods in the day when the heat is at its maximum. These are at eleven 

 A. M. and four p. M. ; and while all observations agree upon this point, the 

 observations of Lichtenfels and Frohlich have shown that these periods are 



