56 THE VEGETABLE PROTEINS 



the fact that this has not yet been accomplished is by no means conclu- 

 sive evidence of the absence of such substances. Molisch's reaction is not 

 given by most of those proteins whose physical properties favour their 

 purification. Preparations of the crystalline globulins from the squash, 

 hemp and flax-seeds and Brazil-nut, the juglansin from the walnut, 

 corylin from the hazel-nut, amandin from the almond, and legumin from 

 the pea or vetch, have been obtained which give no trace whatever of 

 this reaction. On the other hand preparations of other proteins, 

 especially those from the leguminous seeds, frequently give very strong 

 reactions, but it has been noted that when a number of different prepara- 

 tions of one or the other of these proteins are tested under uniform 

 conditions the intensity of the reaction varies greatly. In such cases 

 it is highly probable that this reaction is caused by a small amount of 

 some contaminating substance which is difficult to separate from the 

 protein. 



D. Nitrogen in Vegetable Proteins. 



Partition of Nitrogen in Seed Proteins. 



The different forms in which the several seed proteins yield their 

 nitrogen when completely decomposed by boiling with strong hydro- 

 chloric acid has been extensively studied by Osborne and Harris (349). 



Hausmann's method (150), slightly modified, was used for these 

 determinations, the results of which are given in the table (p. 57), 

 together with a few obtained with animal proteins which are introduced 

 for the sake of comparison. 



The most striking feature shown by this table is the wide range in 

 the amount of basic nitrogen obtained from the different proteins, namely, 

 from one-third to one-thirtieth of the total nitrogen of the protein, while 

 the proportion of ammonia differs from one-fourth to one-sixteenth of 

 the total nitrogen. The non-basic nitrogen, on the other hand, is more 

 constant even than the total nitrogen and forms from about one-half to 

 three-fourths of the latter. 



Comparison of the Nitrogen Precipitated by Phosphotungstic Acid 

 with that in the Basic Ammo-acids. 



The great differences thus indicated in the constitution of these 

 different proteins make it important to know with what accuracy such 

 figures as these in the table (p. 57) can be obtained. Unfortunately 

 there is no method by which they can be directly tested, but the 

 constancy of the results can be established and indirect evidence ob- 

 tained which makes it highly probable that they closely agree with 



