98 HOW CROPS GROW. 
vegetable albumin. The clear juice of the potato tuber 
(which may be procured by grating potatoes, squeezing 
the pulp in a cloth, and letting the liquor thus obtained 
stand in a cool place until the starch has deposited,) con- 
tains albumin in solution, as may be shown by heating to 
near the boiling point, when a coagulum separates, which, 
after boiling successively with alcohol and ether to remove 
fat and coloring matters, is scarcely to be distinguished, 
either in its chemical reactions or composition from the 
coagulated albumin of eggs. 
The juice of succulent vegetables, as cabbage, yields 
vegetable albumin in larger quantity, though less pure, by 
the same treatment. 
Water which has been agitated for some time in contact 
with flour of wheat, rye, oats, or barley, is found by the 
same method to have extracted albumin from these grains. 
The coagulum, thus prepared from any of these sources, exhibits the 
reactions characteristic of the albuminoids, when put in contact with 
nitrate of mercury, nitric or chlorhydric acids. 
Exp. 47,—Prepare impure vegetable albumin from potatoes, cabbage, 
or flour, as above described, and apply the nitrate of mercury test. 
Fibrin.— Blood-Fibrin.—The blood of the higher ani- 
mals, when in the body or when fresh drawn, is perfectly 
fluid. Shortly after it is taken from the veins it partially 
solidifies —it coagulates or becomes clotted. It hereby 
separates into two portions, a clear, pale-yellow liquid— 
the serum, and the clot. As already stated, the serum 
contains albumin. The clot consists chiefly of fibrin. On 
squeezing and washing the clot with water, the coloring 
matter of the blood is removed, and a white stringy mass 
remains, which is one form of the substance in question. 
Blood-fibrin is not known in the soluble state, except in 
fresh blood, from which it cannot be separated, ag it so 
soon coagulates spontaneously. 
Prepared as just described, fibrin has many of the proper- 
ties of albumin. Placed in 4 solution of saltpeter, espe- 
