NUTRITIVE PRINCIPLES OF PLANTS. 253 
may be observed; the upper contains the oil, the under what- 
ever is soluble in water. Boiling precipitates coagulated albu- 
men from this aqueous solution ; casein remains in the hot liquid, 
and may be removed by acetic acid. The albumen of sweet 
almonds is remarkable for its solubility, and for its property of 
causing the decomposition of amygdalin. When these almonds 
are well freed from oil by expression, treated with ether, and 
washed with cold water, acetic acid throws down casein from 
the aqueous solution, leaving albumen. It was this property 
which induced Robiquet to give a peculiar name to the albumen 
from that source. 
Coagulated vegetable albumen is obtained from sweet al- 
monds, when they are peeled, grated, and boiled a few minutes 
in water, which removes the sugar, gum, and the chief part of 
the casein, then washed with ether to remove the oil. In all its 
properties, in all its combinations, and in its behaviour towards 
acids and alkalies, it resembles the coagulated white of the ege. 
When burnt, these almonds leave 3°17 per cent of ashes, con- 
taining a great deal of carbonate of potash, besides phosphates of 
magnesia and lime, with traces of iron and alkaline phosphates. 
These same salts are found in milk, and it is scarcely to be 
doubted that the potash in both is in combination with the casein 
and albumen. It is generally believed that the alkali of milk is 
in combination with lactic acid, but that acid has never been 
found in it when new. It is known that the acid in question be- 
gins to form as soon as milk leaves the udder, that it increases 
until the alkaline combinations are destroyed, and the conse- 
quence is coagulation, and the formation of lactate of casein, or 
cheese. Wheaten flour contains a considerable quantity of 
vegetable albumen, which may be extracted by cold water, and 
coagulated by boiling. 
The juice of plants of every kind, when boiled, gives more or 
less coagulated albumen, of a gray or green colour; in most 
cases it is mixed with the green colouring matter of the leaves, 
and a colourless crystallizable fat or wax. There is a very great 
quantity of albumen in the juice of carrots, turnips, stalks of 
peas, cabbages, and garden vegetables in general. 
Gluten is the name given to that part of the viscous matter of 
wheaten flour, which is soluble in alcohol. The alcohol is eva- 
porated off, and the gluten remaining washed with hot water ; 
it is a soft, yellowish mass, very viscous, and always somewhat 
acid in its action. 
