404 NUTRITION. 



be raised so much ; that is to say, one-third of a degree, 

 when we respire air at the temperature of the blood and 

 saturated with the vapor of water, all loss of heat then being 

 impossible." l In numerous experiments performed on this 

 principle, Prof. Lombard failed to observe a sufficiently 

 marked elevation of temperature to justify the conclusion 

 that the blood is ordinarily cooled in passing through the 

 lungs. These experiments cannot be so positive as those 

 made by introducing thermometers into the heart in living 

 animals without opening the chest or disturbing the circu- 

 lation ; but they are important, in connection with such 

 observations, as failing to prove that the blood is either 

 cooled or heated in the lungs. 



From these facts it appears that there is no positive evi- 

 dence of any change in the temperature in the blood in pass- 

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

 probably exist no constant differences in temperature in the 

 two sides of the heart. "When the loss of heat by the gen- 

 eral surface is active, as in animals with a slight covering of 

 hair, the blood is generally cooler in the right cavities ; but 

 in animals with a thick covering, that probably lose a great 

 deal of heat by the pulmonary surface, the blood is cooler on 

 the left side. There can be no doubt that there are refri- 

 gerating influences in the lungs, both from the low tempera- 

 ture of the inspired air and evaporation ; but these are 

 equalized and sometimes overcome by processes in the blood 

 itself; although, as we shall see hereafter, the lungs are by 

 no means the most important organs of calorification. 



Variations at different Periods of Life. The most im- 

 portant variations in the temperature of the body at different 

 periods of life are observed in infants just after birth. Aside 

 from one or two observations, which are admitted to be ex- 



1 LOMBARD, RechercJm experimentales sur V influence de la respiration sur la 

 temperature du sang dans son passage d travers le poumon. Archives de physi' 

 ologie, Paris, 1869, tome ii., p. 7. 



