ANIMAL HEAT AND FORCE 399 



is o.i8to 1.44 Fahr. (0.1 to 0.8 C.) higher than in the portal veins. 

 This shows that the blood coming from the liver is warmer than in any 

 other part of the body. As regards the temperature of the blood in the 

 two sides of the heart, experiments on the lower animals have been 

 somewhat contradictory ; but there is no positive evidence of any con- 

 siderable change in the temperature of the blood in passing 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 usually is cooler in the 

 right cavities ; 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 vari- 

 ations in the temperature of the body at different periods of life are 

 observed in infants just after birth. The body of the infant and of 

 young mammalia removed from the mother presents a diminution in 

 temperature of i 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 tem- 

 perature of the child nearly reaches the standard in the adult, and the 

 variations produced by external conditions are not so great. 



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 diminishes when they are removed from 

 the body of the mother, and they then become reduced to a condition 

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

 this change in temperature can 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 

 (W. F. Edwards). 



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

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

 temperature of the body is not notably reduced, the power of resisting 

 refrigerating influences is considerably diminished. 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 

 body-temperature is modified by the same influences and in the same 

 way as in the male. 



Variations at Different Times of the Day, etc. Although the limits 

 of variation in the body-temperature are not very wide, certain fluctua- 

 tions are observed, depending on muscular repose or activity, diges- 

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



