NITROGENOUS ORGANIC CELL-CONSTITUENTS. 95 



its general properties coincide with those of legumin. It is distinguished 

 from it, however, by being more soluble than legumin in dilute acids. A 

 substance analogous to vitellin has also been found in the seeds of 

 various plants. It is also termed crystallized vegetable casein. 



Gluten, or vegetable fibrin, exists in a large number of grains, par- 

 ticularly those of the cereals, and plays an important part in the nutritive 

 value of vegetable foods. It also exists in the growing parts of plants 

 and in various vegetable juices. It is a compound albuminous body, 

 which differs from all others in that it is soluble in water and in alcohol 

 when traces of free acid or alkali are present. It is only partly and 

 imperfectly soluble in pure water. It may be readily obtained by 

 washing flour under a stream of water, by which the starch is removed, 

 and the gluten then remains in the form of an elastic, grayish mass. 

 Gluten is only partly soluble in alcohol. According to Ritthausen, 

 gluten contains at least four albuminous substances in addition to 

 vegetable albumen, which has been already described ; a body insoluble 

 in alcohol, which is gluten-casein „or the vegetable fibrin- of Liebig, and 

 three nitrogenous substances soluble in alcohol, to which the name of 

 gluten fibrin, gliadin, and mucedin have been given. 



1. Gluten-Casein. — To prepare this body, fresh gluten is washed first 

 with alcohol, and the insoluble residue is then agitated with two-tenths of 

 one per cent, potash solution, which dissolves out the gluten and leaves an 

 insoluble residue of starch and iaXty matters. From the fluid gluten- 

 casein is precipitated in floceuli by the addition of acetic acid sufficient 

 to give a faint acid reaction. It is then washed with water and alcohol, 

 and after desiccation the gluten-casein so prepared is insoluble in hot 

 and cold water. Boiling water, however, causes it to undergo some 

 modification, which renders it insoluble in alkalies and acids. In the 

 fresh state it is soluble in acetic acid, and in alcohol acidulated with 

 acetic acid. All weak alkaline solutions dissolve fresh gluten-casein, 

 and cause it when dry to first swell up and then dissolve. It is precipi- 

 tated out of these solutions by acids and the mineral salts, forming 

 combinations with the latter. Its properties are very similar to those of 

 legumin and conglutin. It contains more sulphur and less nitrogen 

 than legumin. 



2. Gluten-Fibrin. — This body is obtained by distilling the alcoholic 

 solution of gluten until the fluid does not contain more than 40 percent, 

 of alcohol ; a mucilaginous mass rich in gluten-fibrin is then deposited, 

 and may be purified by washing with absolute alcohol and precipitating 

 with ether. It then forms a coherent, tenacious mass, insoluble in water. 

 Its separation from the gliadin and mucedin of gluten depends upon the 

 fact that all are soluble in dilute alcohol, and that gluten-fibrin is almost 

 insoluble in water and very weak alcohol. As the alcohol is distilled off 



