98 HOW CROPS GROW. 



I 



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 acid-. 



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, as it so 

 soon coagulates spontaneously. 



Prepared as just described, fibrin has many of the proper- 

 ties of albumin. Placed in a solution of saltpeter, espe- 



