74 THE VEGETABLE PROTEINS 



precipitated by saturation with these salts, and can be included in the 

 group of albumins only on the basis of their solubility in water at 

 neutral or slightly acid reaction and their coagulability by heat. It is 

 not always easy to decide whether, or not, a vegetable protein actually 

 belongs with the albumins, as it is difficult, in many cases, to determine 

 whether the protein substance in question is soluble in water alone or 

 whether the presence of minute quantities of salts, bases or acids has 

 caused its solubility. Thus, some leguminous seeds contain legumelin, 

 which appears to be soluble in pure water but is partially precipitated 

 by long-continued dialysis. Such precipitates, however, are not soluble 

 in saline solutions and it is probable that they result from a denaturing 

 of the protein. Whether in these cases denaturing occurs before pre- 

 cipitation, or the precipitation results from a complete removal of the 

 salts and denaturing occurs after precipitation, is difficult to establish, 

 and doubt exists, therefore, in regard to the real solubility of such pro- 

 teins. Owing to the small quantity in which albumins have thus far 

 been obtained from seeds, and the difficulties presented in completely 

 separating them from associated globulins, conclusive evidence in re- 

 gard to the albumin nature of some of them has not yet been obtained, 

 and they must, for the present, be regarded as albumins since their 

 properties seem to agree best with those characteristic of this group. 

 Leucosin of wheat has been most carefully studied in respect to its 

 solubility in water, and it has been found to be completely soluble in 

 solutions which contain but a mere trace of mineral matter. Most 

 seeds and, probably, most plant juices yield proteins which are as well 

 entitled to be placed in the group of albumins as any of those of animal 

 origin. The best characterised vegetable albumins are : 



{Wheat, Triticum vulgare (366, 336). 

 Rye, Secale cereale (304). 

 Barley, Hordeum vulgare (305). 

 Pea, Pisum sativum (330). 

 Horse-bean, Viciafaba (332). 

 Vetch, Vicia sativa (333). 



Legumelin (334) found in the seeds of 



Soy-bean, Glycine hispida (335). 



Lentil, Ervum lens (331). 



Adzuki-bean, Phaseolus radiatus (329). 



Cow-pea, Vigna sinensis (327). 

 Phaselin found in the seeds of Kidney-bean, Phaseolus vulgaris (303). 



Ricin ,, ,, ,, Castor-bean, Ricinus communis (365). 



Small quantities of albumins are also found in most other seeds 

 but have not been studied or given distinctive names. 



($) Globulins. 



That seeds contain protein matter soluble in neutral saline solutions 

 was first shown by Denis (88), and later confirmed by Hoppe-Seyler 



