ULTIMATE CONSTITUENTS OF THE BODY. 



85 



minute quantity of phosphate of lime associated with it. By boiling, 

 and so dissolving, either of these substances in a solution of caustic 

 potash, its sulphur is removed from it; and when the animal substance 

 is reprecipitated in a solid form by acetic acid, its composition is al- 

 tered only by the loss of sulphur. This desulphurized substance, 

 the same in character whether obtained from albumen, fibrin, or case- 

 in, was supposed by Mulder to be the true basis of each of these 

 three substances, which differed only, according to this view, in the 

 relative quantities of sulphur which they contained. This common 

 hypothetical base was accordingly named by him protein (from /OWT^TT, 

 protos, first) ; and the albumen, fibrin, and casein were regarded as 

 compounds of protein with sulphur, and were designated proteinaceous 

 substances. Protein, however, is an artificial product, the result of a 

 very violent chemical action ; and it cannot be admitted as an actual 

 constituent of the body. On this and other grounds, the protein 

 theory is not now generally accepted ; and it is considered better to 

 regard albumen, globulin, syntonin, fibrin, and casein, as closely al- 

 lied bodies, of which albumen is the type, so that they may be called 

 albuminous or, better, albuminoid substances. 



As to the other azotized bodies, in the first place, gelatin seems to 

 be a modification of, or derived product from, albumen, the sulphur 



