24 Professor Liebig on the 



the fodder contains. As regards the milch cow in parti- 

 cular, the butter in the milk corresponds very nearly with the 

 quantity of fatty material contained in its food ; at least as 

 far as in that of the food we have yet studied, namely hay 

 and Indian corn, which last the cow does not usually obtain 

 as food." 



After the foregoing facts, which I could considerably mul- 

 tiply, it will be very difficult for MM. Dumas and Payen to 

 prove that the cow, for instance, furnishes from the fatty 

 matter contained in the food only the corresponding quantity 

 of butter. The proof of the supposition, besides, that animals 

 receive the fat in their food in the same state as it is found 

 in their bodies, is impossible. Nothing is easier to decide 

 than the question whether or not the butter which the cow 

 produces, is contained as butter in the hay. 



Hay gives after exhaustion by aether a green solution, and 

 on evaporation a green residue, with a strong agreeable smell 

 of hay, which possesses no properties characteristic of fatty 

 substances. This green residue consists of various substances, 

 of which one is of a waxy or resinous nature, known under 

 the name of chlorophyll ; another ingredient of the same 

 crystallises from a concentrated aethereal solution in minute 

 laminae, and is the crystalline wax which Proust obtained from 

 plums and cherries, from the leaves of cabbages, from a spe- 

 cies of Iris, and from grasses, and which is probably identical 

 with the wax that Avequin collected in such large quantities 

 from the leaves of the sugar-cane. M. Dumas has analysed 

 this substance, and found it to differ both in composition and 

 properties from any of the known fats ; in consequence of which 

 he felt justified in giving the name cerosine to this substance. 



M. Presenilis obtained by means of aether from straw, and 

 M. Jagle, of Strasburg, from the fresh plant, Fumaria offici- 

 nalis (in the Giessen laboratory), by means of alcohol, a cry- 

 stalline wax, very similar to cerosine. The occurrence of wax 

 in the vegetable kingdom is very extensive, generally ac- 

 companied by chlorophyll. 



Margaric or stearic acid, the principal ingredient of the fat 

 of animals, is neither found in the seeds of corn, nor in herbs 

 nor in roots which serve as food. It is evident that if the 

 ingredients of the food soluble in aether are convertible into 

 fat, margarine and stearine must be formed out of wax or 

 chlorophyll. 



As far as our experience goes, the chlorophyll of the food 

 taken in a green state is given out from the body unchanged; 

 even in man the excrements retain the colour of the green 

 vegetables consumed. It is also considered that the wax does 



