420 NUTKITION. 



regards the amount of heat generated, of the processes of 

 nutrition, as we can study them separately ? 



3. What are the principles invariably and of necessity 

 consumed and produced in the organism in calorification ; 

 and what is the relative importance of the principles thus 

 consumed and the products thus generated and thrown off? 



4. How far have we been able to follow those material 

 transformations in the organism, which involve the consump- 

 tion of certain principles, the production of new compounds, 

 and the generation of heat ? 



Seat of the Production of Animal Heat. Few if any 

 physiologists at the present day hold to the opinion that 

 there is any part or organ in the body specially and exclu- 

 sively concerned in the production of heat. In the early his- 

 tory of the oxidation-theory of Lavoisier, it was thought by 

 some that the inspired oxygen combined with the hydro- 

 carbons of the blood in the lungs, and that the heat of 

 the body was generated almost exclusively in these organs ; 

 but this idea has long since been abandoned. We have 

 already f ally considered the question of loss or gain in the 

 temperature of the blood in its passage through the lungs, 

 and have seen that there is, to say the least, no constant 

 elevation showing a generation of heat in these organs, suffi- 

 cient to warm the blood, and through it the different parts 

 of the body. If we find that the blood in coming from 

 the lungs has about the same temperature as when it en- 

 tered, it must be admitted that there is a certain generation 

 of heat to compensate the loss by evaporation from the pul- 

 monary surface. As far as we know, the heat that results from 

 the mere physical solution of oxygen in the blood is all that 

 is produced in the lungs. It is, indeed, estimated by Mar- 

 chand, that the fixation of oxygen in this way is marked by 

 an elevation of nearly 2 Fahr. 1 There is no sufficient evi- 



1 MARCHAND, Ueber die Einwirkung des Sauerstoffs auf das Blut und seine 

 Bcstandtheile. Journal fur praktische CJiemie, Leipzig, 1845, Bd. xxxv., S. 400. 



