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LIEBIG REVIEWED. 
lular tissue, nervous matter, and bones, must derive their origin 
from the nitrogenized constituent of milk. 
Our next inquiry will be whence these substances are derived 
in graminivorous and herbivorous animals. 
When the newly expressed juices of vegetables are allowed to 
stand, a separation takes place in a few minutes; a gelatinous 
precipitate, commonly of a green tinge, is deposited, and this, 
when acted on by liquids that remove the colouring matter, 
leaves a greyish-white substance, well known to druggists as the 
deposit from vegetable juices. This is one of the nitrogenized 
compounds which serves for the nutrition of animals, and has been 
named vegetable fibrine. Again; when the clarified juices of nu- 
tritious vegetables, such as cauliflower, asparagus, mangel, and 
turnips, are made to boil, a coagulum is formed, which it is abso- 
lutely impossible to distinguish from the substance that separates 
as a coagulum, when the serum of blood or the white of an egg 
diluted with water are heated to the boiling point. This is ve- 
getable albumen. 
The third nitrogenized constituent of the vegetable food of ani- 
mals is vegetable caseine. This substance is chiefly found in the 
seeds of peas, beans, and other leguminous plants. When these 
seeds are softened in water, then ground with that fluid, and the 
mass farther diluted and strained through a fine sieve, there passes 
through it a solution of caseine, in which starch is suspended. 
When the starch has settled, the supernatant liquor is a solution 
of caseine, which is always like milk, turbid, partly from sus- 
pended fat and partly from the gradual action of the air on the 
dissolved caseine, lactic acid being slowly formed, which causes a 
gradual separation. 
Until very recently it was believed that vegetable albumen, 
fibrine, and caseine, differed from animal albumen, fibrine, and 
caseine; but the recent discoveries of Muller have shewn that 
this opinion was erroneous. Liebig has demonstrated that caseine 
exists in vegetables with all the characters of that found in milk. 
But the more important step recently made in this peculiar and 
very important investigation is, doubtless, the discovery made by 
Muller, that albumen, fibrine, and caseine, are all nothing more 
than modifications of a compound to which he has given the 
name of proteine (from tqwtevco, I take the first place), as being 
the original matter from which all other varieties are derived. 
Proteine is composed of carbon, hydrogen, nitrogen, and oxygen ; 
and Muller has shewn that two analyses of proteine do not differ 
more than analyses of fibrine, albumen, or caseine do, either from 
one another, or from that of proteine, as far as regards their ele- 
ments. He has farther shewn that all these bodies, whether they 
