358 



PRINCIPLES OF AGRICULTURAL CHMISTPY 



acid. Proteoses and peptones are formed in the digestion of 

 proteids within the animal body, by the action of the juices of the 

 stomach (the gastric juice), which contain pepsin, upon them. 



Proteids in Plants. The names and occurrence of some plant 

 proteids are as follows : 



Legumin, which is found in considerable quantity in seeds of 

 pea, horse bean, vetch, and lentil. 



Vignin, the chief protein of the cowpea. 



Glycenin, a globulin, chief protein compound of soy bean. 



Gliaden, soluble in alcohol of 70-80 per cent., the most abundant 

 protein of wheat kernels. 



Hordein, soluble in alcohol, found in barley. 



Zein, most abundant in corn, easily soluble in alcohol. 



Vicilin, a globulin found in pea, lentil and horse bean. 



Composition of Proteids. The proteids vary in composition 

 and properties. The percentage composition of some important 

 vegetable proteids is given in the following table i 1 



The factor 6.25 used for proteids requires 16.00 per cent, nitro- 

 gen. The above proteids contain from 17.20 to 18.30 per cent, 

 nitrogen. 



Amides and Amido Compounds. Amides, as distinguished from 

 proteids, are nitrogenous compounds of known molecular weights 

 and known constitution. They have little value in animal nutri- 

 tion. 



In seeds they occur only in small quantity. They are more 

 abundant in leaves and the growing parts of plants, and are parti- 

 cularly abundant in germinating seeds. Nitrogenous material is 

 converted into amides for the purpose of transportation through 

 1 Osborne, The Vegetable Proteins, p. 49. 



