4 THE VEGETABLE PROTEINS 



In 1819 Taddei (537) separated wheat gluten into two well-charac- 

 terised parts, one of which, soluble in alcohol, he called gliadin, the 

 other, insoluble therein, zymom. By this observation three distinct 

 proteins were shown to be present in wheat flour. 



Gorham (135) described, in 1821, a protein soluble in alcohol which 

 he obtained from the seeds of maize and to which he gave the name 

 zein. A year later Bizio (37, 38) described the results of his investi- 

 gation of this seed, and stated that zein was a mixture of- gliadin and 

 zymom, which Taddei had then recently found in wheat gluten, together 

 with fat, and he regarded this mixture as similar to the gluten of 

 wheat. 



Braconnot (54) in 1827 described the protein constituents of some 

 leguminous seeds. He named the protein which he obtained from 

 them legumin and showed that it formed salt-like combinations with 

 acids. 



During the next few years little further progress was made in the 

 study of plant proteins (cf. 256, 34, 35, 584, 55, 56, 57, 158, 44, 133). 

 Up to this time the knowledge of vegetable proteins had extended 

 only to a recognition of their general occurrence in plants and to a more 

 or less crude description of their physical properties and solubility. 



In 1836 Boussingault (51) published elementary analyses of several 

 plant proteins which marked a new epoch in the development of their 

 study, for these analyses were soon followed by those made in 1839 

 by Mulder (283) and by those made by Liebig and his pupils in 1841 

 and the years immediately following (cf. 223, 551, 451, 181, 155, 433, 

 434, 224). Apparently largely on the ground of these analyses, which 

 agreed closely with those obtained with animal proteins, Liebig as- 

 serted in 1841 (223) that the different forms of plant proteins known 

 at that time were identical with the proteins of animal origin which 

 bore similar names. He recognised four such substances, namely, 

 vegetable albumin, plant gelatin, legumin or casein, and plant fibrin. 

 Throughout the previous history of the development of knowledge 

 of plant proteins and up to the time of Liebig, the idea of their identity 

 with the animal proteins appears to have been universally accepted, and 

 every effort had evidently been made by those who studied them to 

 discover similarities between the proteins from these two sources. In 

 the year following, however, Dumas and Cahours (97) presented the 

 results of an elaborate study of the elementary composition of a con- 

 siderable number of animal and vegetable proteins, which formed the 

 foundation of a new advance in the knowledge of protein substances 

 in general and contributed especially to the future studies of the pro- 



