488 PHYSIOLOGY AT THE FARM. 



integration more particularly occurs in the muscular fibres so 

 largely concerned in the operations of the animal economy. 

 It is continually going on in the acts concerned in what was 

 termed above, vital work that is, in the contraction of the 

 heart and blood-vessels, and in the processes of respiration and 

 assimilation ; and even when the body is at rest, not a few of 



subservient to assimilation. Starch, sugar, oil, albumen, do not 

 escape digestion in the stomach, duodenum, and the organs inter- 

 posed between the alimentary canal and the system of the venous 

 blood. And even were it allowed that sugar and oil, existing in 

 the venous blood in no closer approach to vitality than as being 

 products of lifeless organic matter, are the source of animal heat, 

 when burnt with the oxygen of respiration, it is plain that the 

 supply of such materials would be but occasional, that is, for a 

 period after each meal, and not constant, like the unceasing com- 

 petency of a living body to afford animal heat and muscular 

 energy, not always slackening even at the moment when death is 

 at hand. If, then, the blood be largely and constantly concerned 

 in the production of animal heat and muscular energy, it must be 

 by the disintegration of its organic constituents in the presence 

 of the oxygen received in respiration; in which case a long- 

 debated question must recur namely, whether the carbonic acid 

 expelled in expiration be formed exclusively in the lungs, or 

 partly in the lungs and partly in the capillaries throughout the 

 body. If the animal heat and the heat to be metamorphosed into 

 muscular energy be the result of the combustion of semi-assimilated 

 aliment newly brought from the digestive organs, aided by the 

 disintegration of the organic constituents of the blood itself, then 

 all that heat must be produced within the chest for the portion 

 to be metamorphosed must in that case be sensible heat till it 

 is conveyed to the muscular organs : surely, then, so large an 

 amount of heat developed in the chest would realise the idea so 

 often put forward of old, and burn up the lungs. 



That the blood supplies material for animal heat, in so far as it 

 contains at any time either non-azotised combustible matter, or 

 proteine compounds beyond what the present wants of the living 



