DIGESTION IN THE STOMACH 



or any preparation of pepsin, the gelatinous mass rapidly undergoes 

 solution. If the mixture be boiled and neutralised, immediately 

 after solution has occurred, nearly the whole of the protein is thrown 

 down in a coagulated form. The first effect therefore is the 

 production of coagulable soluble proteins from the insoluble fibrin. 

 If the action be allowed to proceed for some hours, a whole series of 

 products of hydrolysis are found in the mixture. On neutralising 

 the fluid, a precipitate may be thrown down consisting chiefly of 

 acid albumen. The greater proportion of the protein remains in 

 solution. This remainder may be purified from any unaltered coagu- 

 lable protein by boiling in slightly acid solution and filtering. The 

 filtrate contains a mixture of bodies belonging to the class of hydrated 

 proteins, viz. proteoses and peptones. 



By means of fractional precipitation with ammonium sulphate 

 or zinc sulphate, these mixtures can be subdivided into various 

 substances, although in no case can we be certain that we are dealing 

 with chemical individuals. The Table on p. 770 represents the chief 

 bodies obtained by Pick by this method from ' Witte's peptone,' 

 a commercial preparation containing proteoses and peptones. 



The following careful analysis of the constituents of protoalbumose 

 and heteroalbumose (or protoproteose and heteroproteose) respectively 

 shows that the different proteoses really correspond to different group- 

 ings of the ammo-acids making up the original protein molecule : 



RESULTS OF THE COMPLETE HYDROLYSIS OF HETERO- AND PROTOALBUMOSE 



The results obtained by Pick by hydrolysis of these different bodies 

 .show th#. in the breakdown of protein produced by gastric juice theie 



49 



