100 M. II. ChUtenden — Caseoses, Casein. Dyspeptone, 



It is thus obvious from the foregoing that by the action of trypsin, 

 caseoses are formed of the same general nature as those formed by 

 the action of pepsin-hydrochloric acid, and by hot dilute sulphuric 

 acid, but with higher contents of carbon. 



In other digestions with trypsin, made especially for the prepara- 

 tion of casein peptone, these caseoses were again separated and the 

 foregoing reactions verified. The quantities, however, were too 

 small to admit of their analysis. 



III. Casein peptone ; — from experiments by Charles Norris, Jr., Ph.B. 



Supersaturation of a digestive fluid with ammonium sulphate, 

 under proper conditions, suffices to entirely remove the preliminary 

 products of proteolytic action. Proper conditions, however, are not 

 obtained by simply adding the ammonivim salt to a cold fluid, for as 

 has been already pointed out an additional precipitate of proteose 

 can nearly always be obtained, by heating the cold saturated solution 

 until a thick crust of the ammonium salt forms on the hot fluid. In 

 the present state of knowledge, we assume as peptone any amorphous 

 product of proteolytic action precipitable by alcohol, and not pre- 

 cipitable by heating with ammonium sulphate added to saturation. 

 Unquestionably, the albumose precipitated only by long boiling of a 

 saturated ammonium sulphate solution, is much nearer to true pep- 

 tone than those bodies more easily precipitated, but at present we 

 are not inclined to accept as true peptone any body precipitable by 

 ammonium sulphate under any conditions whatever. In the present 

 series of experiments we have aimed to prepare a casein peptone, 

 by the action of trypsin, entirely free from albumose in order to 

 study its composition and reactions. 



In the digestion of casein with trypsin, described in the preced- 

 ing section, the filtrate from the ammonium sulphate saturation was 

 heated for some time and the slight gummy film of caseose sep- 

 arated, after which as much of the ammonium sulphate as possible 

 was removed by alternate crystallization, treatment with alcohol, etc. 

 The last traces of the ammonium salt were removed by long con- 

 tinued dialysis in running water, and when finally the fluid gave no 

 reaction with barium chloride it was evaporated to a syrup and pre- 

 cipitated with alcohol. The precipitated peptone was freed from 

 any adhering tyrosin and leucin by repeated treatment with boiling 

 alcohol, and finally dried at 110° C. until of constant weight. This 

 proved a long operation. The peptone was so exceedingly Hygro- 

 scopic and held on so tenaciously to the water, that it was only after 



