96 HOW CROPS GROW. 



viz.: salting, pressing, and keeping until the odor and 

 taste of cheese are developed. It is cheaply sold in. the 

 streets of Canton under the name of Tao-foo. Vegetable 

 casein appears to occur in small quantity in the potato, 

 and many plants ; and may be exhibited by adding a few 

 drops of acetic acid to turnip juice, for instance, which 

 has been freed from albumin by boiling and filtering. 



The Globulins are insoluble in water, but dissolve in 

 neutral salt-solutions. Some dissolve only in salt-solu- 

 tions of moderate strength and are thrown down from 

 these solutions by more salt. Others are soluble in sat- 

 urated salt-solutions. They are coagulated by heat. 

 Some animal globulins may first be noticed. 



Vitellin is obtained from the yolk of eggs ; fat and 

 pigment are first removed by ether, and the white residue 

 is dissolved in a solution of common salt (1 of salt to 10 

 of water). Addition of water to the filtered solution 

 separates the vitellin as a white, flocky mass. 



Paraglobulin exists in blood serum, and may be 

 thrown down by saturating the serum with magnesium 

 sulphate. It may be obtained in transparent microscopic 

 disks that are probably crystalline. Its solutions in brine 

 coagulate by heat, like albumin. 



Fibrinogen. When blood fresh from the veins of the 

 horse is mixed directly with a saturated aqueous solution 

 of magnesium sulphate, fibrinogen dissolves, and the 

 liquid, after filtering from the red corpuscles, upon mix- 

 ing with a saturated brine of common salt, deposits this 

 body in white flocks, which unite to a tough, elastic 

 mass. Its solutions in brine coagulate at a lower tem- 

 perature than those of paraglobulin. 



Fresh-drawn blood, after standing a short time, coag- 

 ulates of itself to a more or less firm clot. Under the 

 microscope this process is seen to consist in the rapid 

 formation of an intricate net-work of delicate threads or 

 fibrils. These are fibrin, and come from the coagulation 



