CLASSIFICATION OF VEGETABLE PROTEINS 75 



(167), who found that such substances were extracted from vegetable 

 tissues by solutions of sodium chloride. In 1877 Weyl (569, 570) 

 examined a large number of seeds and found that all of them contained 

 protein soluble in solutions of sodium chloride. He divided the globu- 

 lin thus extracted into two groups, the vitellins, soluble in saturated 

 solutions of sodium chloride, and the myosins, insoluble therein. Vines 

 (561, 563) soon after investigated the action of salt solutions on the 

 aleurone grains in different seeds and proposed a classification of these 

 based on his observations. The criticism made by Weyl of the results 

 which Ritthausen had obtained by extracting seeds with dilute alkalies 

 led Ritthausen to apply extraction with sodium chloride solutions to 

 a number of the seeds which he had previously studied, and he showed 

 that most of the seed proteins were globulins. The experience of all 

 who have since worked with the proteins of seeds has fully confirmed 

 this conclusion. 



Globulins, as here defined, are proteins insoluble in water but 

 soluble in saline sglutipjis. In this group must be included, for con- 

 venience, a large number of vegetable proteins which do not strictly 

 conform to this definition. We have already discussed at some length 

 the effect of combined acid on the solubility of many seed proteins^ and 

 have shown that a number of these have the properties of globulins 

 only when combined with a small amount of acid, as a protein salt, 

 When freed from this acid by complete neutralisation, these proteins 

 are entirely soluble in water and in this condition lack the most essen- 

 tial properties of the globulins. As, by the current methods of pre- 

 paration, these proteins are almost invariably obtained in the form of 

 their salts, it is much more convenient to include them with the globu- 

 lins, for it must be remembered that our present method of classifica- 

 tion has been devised simply for the convenience of those who write 

 and teach about these substances. 



It has been shown that the solubility of edestin chloride depends 

 not only on the proportion of combined acid, but also on the propor- 

 tion of mineral salts contained in the solution. Those preparations 

 which have an acidity to phenolphthalein greater than about 07 c.c. 

 per gramme are soluble in water in proportion to their degree of acidity, 

 while those containing an amount of acid equal to 1*4 c.c. of decinormal 

 alkali are soluble therein. The aqueous solutions of the acid salts of 

 edestin are precipitated by adding to them a small quantity of sodium 

 chloride, or other inorganic salt, and the precipitate, thus produced, 

 dissolves again when the quantity of added salt is sufficiently increased. 

 Such acid compounds of edestin are therefore precipitated by dialysis 



