20 Professor Liebig on the 



disease, or of an increased absorption of oxygen, and its being 

 given out in the form of carbonic acid and water, is a proof 

 that that non-nitrogenous body is converted to the same use 

 as sugar, gum, or starch in animal bodies, and for want of 

 other non-nitrogenous food is applied to the respiration. 



The further consideration, that the flesh of the carnivo- 

 rous, which of all animals eat most fat, contains no fat, and is 

 not eatable ; that the fat in the bodies of graminivorous 

 animals increases when the process of respiration, and with it 

 the absorption of oxygen diminishes, through a want of exercise 

 or an increase of temperature, leads to the conclusion that the 

 fat has its origin in the non-nitrogenous food, the carbon re- 

 maining in the body in the form of fat when there is a defi- 

 ciency of the necessary quantity of oxygen to convert it into 

 carbonic acid. 



Supported by the example of what certainly takes place in 

 the processes of fermentation and putrefaction, in which sugar 

 and starch, by giving out oxygen or carbonic acid, form new 

 combinations, which, like aether and fusel oil, more resemble 

 fat in their properties than any other known compounds, I 

 have endeavoured to trace out the formation of fat, on the 

 supposition that the carbon of non-azotized substances re- 

 mains in the animal body in the form of fat. 



According to my statement, the fat consequently originates 

 from the non-nitrogenous constituents of the food : let us 

 suppose from sugar, then this must have undergone a che- 

 mical change in conformity with my proposition. 



The formation of wax from honey which contains none, in 

 the body of the bee, of which, from the experiments of M. 

 Grundlach of Cassel, there can be no doubt, appears to remove 

 every objection to the possibility of such an action taking 

 place. 



I never had the least idea of defending in my book the opi- 

 nion, or even of expressing it, that the fat which was taken in 

 the food of animals did not contribute to increase the quantity 

 of fat in their bodies; but I was not aware of any supply of 

 butter in the grass which is daily consumed by cows, or of 

 tallow, of lard, or goose-fat in potatoes, barley and oats ; in 

 the analyses of these substances as at present given, they con- 

 tain only waxy substances, and that in such a small quantity 

 that I consider the formation of fat could not be attributed 

 to it. 



These ideas concerning the origin of fat in animal bodies 

 took a new dix-ection from a note which M. Dumas appended 

 in the Annates de Chimie (new Series, vol. iv. p. 208) to 

 my treatise on the nitrogenous food of the vegetable kingdom ; 



