CLASSIFICATION OF VEGETABLE PROTEINS 87 



proteins do not belong to this group, for they give no Molisch reaction 

 and therefore contain no carbohydrate. Krakow (210) obtained an 

 osazone from " pea albumin," but in the absence of conclusive evidence 

 that the preparation of this " albumin " was free from admixed carbo- 

 hydrate, little importance attaches to this observation. Ishii (171) has 

 described a substance obtained from the tubers of yams which had 

 physical properties and an ultimate composition similar to the mucins 

 of animal origin. As he makes no statements concerning the presence 

 of carbohydrate in his preparations its relations to the true mucins are 

 yet to be demonstrated. Wr6bleski (582) has stated that mucin is one 

 of the constituents of yeast, but gives no experimental evidence of this. 

 Several observations are on record indicating that many bacteria pro- 

 duce a mucin-like substance in the culture medium in which they 

 grow, but such substances are hardly to be considered as vegetable 

 proteins. 



(c) Phosphoproteins. 



It seems to be believed by many writers on vegetable proteins that 

 a large number of the proteins of seeds contain phosphorus and should 

 be consequently assigned to the group of phosphoproteins [cf. Wiman 

 (573)]. The fact that the reserve food protein of the egg yolk consists 

 largely of such a phosphorised globulin-like protein, and that the pro- 

 tein of milk consists chiefly of the phosphorised casein belonging to 

 this group, has apparently led many to assume, by analogy, that a 

 large part of the reserve food protein of seeds consists of similar sub- 

 stances (cf. Czapek, 82^, p. 59). 



Hoppe-Seyler (167) suggests the presence of protein substances in 

 the Brazil-nut and pea which may be similar to the vitellin of the yolk 

 of hens' eggs, but he bases this suggestion solely on the fact that he 

 had extracted a lecithin-like substance from crude preparations obtained 

 from these seeds. He says nothing of the presence of phosphorus in 

 the protein which remained after extracting with warm alcohol, and 

 consequently gives no evidence which shows these to be vitellin-like 

 proteins. 



In discussing the relations of edestin to acids it was shown that the 

 preparations of crude edestin which were obtained by a single precipita- 

 tion from the extract of the seeds contained a small amount of phos- 

 phorus, but that this disappeared completely after a second precipitation 

 by dialysis or by dilution. The crude preparations of most seed pro- 

 teins, like those of edestin, contain traces of phosphorus, but, when 



