NITROGENOUS ORGANIC COMPOUNDS OF PLANTS 227 



from plant substances. This albuminoid contains phos- 

 phorus, and has been assigned the formula C^H^NgPgO.j,, 

 Nuclein takes an important part in the growth and life 

 processes of both plant and animal cells. From different 

 sources it has slightly different chemical properties. It 

 is probably a mixture of several bodies, and not a dis- 

 tinct chemical compound. 



310. Gelatin is an albuminoid obtained from connec- 

 tive tissue and bones by the action of either boiling 

 water or dilute acids upon an albuminoid called collagen. 

 Commercial gelatin or glue is the crude product obtained 

 from animal refuse. The formula C TO2 H 151 N 32 O 39 has been 

 assigned to gelatin. Gelatin contains no sulfur, and has 

 a different proportion of nitrogen from that found in 

 proteid bodies. 



311. Mucin is an albuminoid present in connective 

 tissue. It is the chief constituent of mucus, and imparts 

 sliminess to the secretions of the mucous membrane. 

 Mucin is present in the saliva from the submaxillary 

 glands, and in the bile and other fluids of the body, par- 

 ticularly those of an alkaline nature. 



312. Elastin is an insoluble albumoid found in connec- 

 tive tissue. Keratin is the hard, horny material found 

 in nails, hoofs and horns, while chondrin is obtained from 

 cartilage. A number of other albuminoids also are pres- 

 ent in both animal and plant bodies. 



313. Food Value of Albuminoids. Gelatin and 

 most of the animal albuminoids undergo digestion ,J>ut 

 cannot take the place of protein in a ration. An animal 



