26 Professor Liebig on the 



but that they receive all sustenance, whether sugar, starch, 

 or fat, from the vegetable kingdom. 



I agree perfectly in opinion with M. Dumas in relation to 

 the substances which serve for the formation of blood; but 

 differ from him in considering it as fully proved, as far as 

 observation extends, that wax is formed in the body of the 

 bee, and fat in the stall-fed cow. 



In regard to the principle of M. Dumas, that the organism 

 of an animal is not able to produce any substance serving as 

 food, it is equivalent to saying that the organism produces 

 nothing, but only transforms it ; that no combination takes 

 place in its body, when the materials are not present by 

 means of which the metamorphosis originates. Thus the for- 

 mation of sugar of milk in the bodies of carnivorous animals 

 cannot take place, for dog's milk, according to Simon, con- 

 tains no sugar of milk. Thus also fat cannot be produced 

 in their organism ; because, besides fat, they do not consume 

 any non-nitrogenous food. But starch, gum and sugar con- 

 tain, even with their large quantity of oxygen, all the ingre- 

 dients of fatty bodies; and the formation of butter in the body 

 of the cow, and of wax in that of the bee, leave hardly any 

 doubt that sugar, starch, gum, or pectine, furnish the carbon 

 for the formation of the butter or of the wax. 



It is further certain that the brain (Fremy), the nerves, the 

 blood (Lecanu), the faeces, and the yellow of the egg (Chev- 

 reul), contain a substance in considerable quantity with a far 

 smaller proportion of oxygen than the known fatty acids, a 

 substance which hitherto has not been found in the food of 

 graminivorous animals. The formation of cholesterine from 

 fat cannot be supposed without a separation of oxygen or of 

 carbonic acid and water; it must be derived from a substance 

 far richer in oxygen in consequence of a process of decomposi- 

 tion or metamorphosis, which, applied to the case of starch or 

 sugar, explains their conversion into fat in the simplest manner. 



In the before-mentioned note to the observations of M. Ro- 

 manet, M. Dumas attempts, from the facts quoted in the pre- 

 face to my Pathology, to weaken the conclusion to which I 

 had arrived concerning the formation of fat in the animal 

 body. These facts concern the quantity of fat in a goose fed 

 upon Indian corn (maize), which corn 1 have alleged not to 

 contain a thousandth part of fat or fatty substance. The ex- 

 periments of M. Liebig, says M. Donne in the Journal des 

 Debats, are throughout inexact and false, as MM. Dumas 

 and Boussingault have obtained 9 per cent, of a yellow oil 

 from Indian corn, which M. Dumas had the honour to exhibit 

 to the Academy. 



