CLASSIFICATION OF VEGETABLE PROTEINS 73 



(<r) Phosphoproteins. 

 (dQ Haemoglobins. 

 (e) Lecithoproteins. 

 III. Derived Proteins. 



1. Primary Protein Derivatives. 



(a) Proteans. 



(b} Metaproteins. 



(c) Coagulated proteins. 



2. Secondary Protein Derivatives. 



(a) Proteases. 

 (b} Peptones. 

 (c) Peptides. 



The vegetable proteins belong to groups which were first established 

 in connection with studies of animal proteins, but the definitions of 

 these groups, as usually found in text-books dealing with proteins, 

 must be modified to some extent if they are to include those vegetable 

 proteins which have properties in the main agreeing with those of the 

 animal proteins heretofore assigned to such groups. The properties 

 of the various vegetable proteins which are here included in the different 

 groups must, therefore, be considered somewhat in detail. 



I. SIMPLE PROTEINS. 

 (a) Albumins. 



After Beccari's discovery of the existence of a protein substance in 

 wheat flour, the presence of coagulable protein was soon recognised in 

 the juices from many parts of different plants. The similarity of this 

 substance to the albumin of hen's egg caused it to be long known as 

 albumin. After advances had been made in the study of the proteins 

 the term albumin was restricted to those proteins which are soluble in 

 water and coagulable by heat. It has, however, of late years become 

 a nearly universal practice among physiological chemists to classify 

 the albumins and globulins on the basis of their behaviour towards a 

 half-saturated solution of ammonium sulphate, and to consider that 

 albumins remain dissolved when this salt is added in this proportion 

 to their solutions. Such a method cannot be employed in differen- 

 tiating those vegetable proteins which are here considered to be al- 

 bumins, for some of them at least are thus precipitated by ammonium 

 sulphate. The animal albumins are not precipitated by saturating 

 their neutral solutions with sodium chloride or with magnesium sul- 

 phate. The vegetable albumins on the other hand are, in many cases, 



