90 HOW CROPS GROW. 



Serum Albumin occurs dissolved in the blood, in milk, 

 and in nearly all the liquids of the health}' animal body ex- 

 cept the urine. Its characters are slightly different from 

 those of egg-albumin. The albumin of the blood may 

 be separated by heating blood-serum (the clear yellow 

 liquid that floats above the clot). The albumin of milk 

 coagulates when milk-serum (whey) is heated to near 

 boiling. 



On boiling entire milk, albumin coagulates, and, mixed 

 with fat and casein, is deposited as a tough coating on 

 the sides of the vessel. 



Animal albumin remains, when its solutions are evap- 

 orated at a temperature below 140 F., as a yellowish trans- 

 lucent and friable solid, which easily dissolves in water. 



Vegetable Albumin. In the juices of all plants is 

 found in small quantity a substance which agrees in 

 many respects with animal albumin, and has been termed 

 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 such a body in solution, as may be shown by heat- 

 ing to near the boiling point, when a coagulum separates, 

 which, after boiling successively with alcohol and ether 

 to remove fat and coloring matters, in its chemical reac- 

 tions and composition closely approaches the coagulated 

 albumin of eggs. 



The juice of succulent vegetables, as cabbage, yields 

 a similar substance in larger quantity, though less pure, 

 by the same treatment. 



Water which has been agitated for some time in con- 

 tact with flour of wheat, rye, oats, or barley, is found 

 by the same method to have extracted an albuminoid from 

 these grains. 



The coagulum, thus prepared from any of those sources, exhibits the 

 reactions characteristic of the albuminoids, when put in contact with 

 nitrate of mercury, nitric or hydrochloric acid. 



