VIII. PROTEIN COMPOUNDS. 



THE name, protein compounds, is applied to certain 

 nitrogenized substances, very similar to each other, 

 which are widely distributed in the animal and vege- 

 table kingdom. 



formation. Only in plants. The animal organism 

 receives these most important ingredients ready formed 

 in the food, and it has only power to assimilate them, 

 and to cause multitudinous metamorphoses in them. 



Composition. This is for all protein compounds so 

 similar that one might be led to suspect that it is the 

 same, and that the variations found are merely caused 

 by the presence of other substances, which they con- 

 tain to a certain extent in organized intertexture, and 

 from which they have not as yet been separated. 

 They all contain carbon, hydrogen, nitrogen, oxygen, 

 and sulphur, but the latter in such small quantity that 

 it is impossible to express its presence by means of a 

 probable formula. The following composition of albu- 

 men gives a representation of the composition of these 

 bodies: *&'?*&* 



Carbon 53.5"per cent/ 3 



Hydrogen .... 7.0 ^ 



Nitrogen . . . . 15.5* " v^' 



Oxygen 22.4 



Sulphur ..... 1.6 



Properties. Most protein compounds can apparently 

 exist in two conditions: a soluble condition, in which 

 they usually occur in nature, and an insoluble or 

 coagulated condition, into which they are converted 



* 



