Chemical Constituents of the Animal Body. 235 



precipitated by salts, they are washed with salt solution 

 of the same concentration as that of the solution in which 

 they have been precipitated, and then freed from the salt 

 by dialysis. From the aqueous solution thus obtained, 

 they can be prepared either by evaporating off the water 

 at a temperature not exceeding 40 or by the addition of 

 alcohol or acetone, in which liquids they are insoluble. 

 They are then washed with aqueous alcohol, then with 

 more concentrated aqueous alcohol, then with absolute 

 alcohol and ether, and finally dried in vacuo. They 

 should not be allowed to remain too long in presence of 

 alcohol, as they are apt to undergo change which renders 

 them insoluble in water. 



The globulins are found in some animal fluids, such as 

 blood-serum, and are held in solution owing to the pres- 

 ence of the salts which these fluids contain. When the 

 solutions are submitted to dialysis, or diluted sufficiently, 

 these globulins are precipitated. When dilution is used 

 as a means of precipitation, the process is facilitated by 

 slight acidification of the liquid with weak acids (such as 

 acetic or carbonic acids). 



In the case of the vegetable globulins, which occur 

 in many seeds, such as hemp seed, various beans, etc., the 

 finely ground dry material is first extracted with ether 

 or light petroleum to separate the fats. The fat-free 

 powder is then treated with saline solution. In the case 

 of hemp seed, the protein, known as edestin, can be 

 obtained in a crystalline form. To prepare the protein 

 in this state, the fat-free powder is extracted with saline 

 solution (usually 6 per cent.) warmed to 60 ; the warm 

 solution is then diluted with water, also warmed to 60, 

 and the mixture allowed to cool. Other plant pro- 

 ducts yield crystalline proteins, which are prepared in 

 a similar manner. The chief prolamine, the gliadin of 



