Chittenden — Caseoses, Casein Di/speptone, and Casein Peptone. 67 



admixture of fat. Judging from tiie description, substance A must 

 have been an acid compound of the body studied, mixed witli more 

 or less undigested casein ; while substance J^ was doubtless a mixture 

 of fat and the body -1. However this may be, our results show 

 conclusively that no body having the formula ascribed by Lubavin 

 to his substance A, can be separated IVom the undigestible residue 

 of casein in pepsin-hydrochloric acid. 



In all of the experiments to be described, the casein employed was 

 freshly prepared from skim milk by precipitating the greatly diluted 

 fluid with dilute acetic acid, washing thoroughly with water, redis- 

 solving the precipitate in water containing a trace of ammonia and 

 reprecipitating, repeating this operation three or four times. 



In subjecting casein to the action of artificial gastric juice the con- 

 ditions were varied more or less in the individual experiments, so 

 that if the so-called dyspeptone be a mixture of two or more sub- 

 stances, the varying conditions under which the digestions were 

 made might so change the nature of the mixture, that on analysis, it 

 would become apparent. 



Digestion A. 



The casein from five gallons of milk was placed in four litres of 

 0"4 per cent, hydrochloric acid and warmed to 40° C. To this was 

 added 200 c. c. of a dialyzed pepsin solution, prepared from a glyc- 

 erin extract of the ferment, and the mixture kept at 40-45° C. for 

 forty-eight hours. At the end of this time there was still a compara- 

 tively large mass of gelatinous matter undissolved, composed in part 

 no doubt, of swollen casein. The entire mixture was then dihited con- 

 siderably with water and treated with dilute alkali to near neutraliza- 

 tion, leaving the fluid, however, distinctly acid. The undio-ested 

 matter was then filtered ofl" and washed thoroughly with water. This 

 partial neutralization of the digestive mixture was found necessary, 

 owing to the extreme slowness with which the acid fluid filtered. 

 The undigested matter was again warmed at 40° C. for forty-eight 

 hours, with four litres of a much more vigorous pepsin mixture con- 

 taining 0*4 per cent, hydrochloric acid. The residue still undissolved 

 was filtered off and washed with water. The acid filtrate gave no 

 precipitate whatever on neutralization. A third time the undigested 

 matter was warmed at 40° C. for sixty hours, with four litres of a still 

 stronger artificial gastric juice. The cpiantity of insoluble matter did 

 not appear to be diminished at all by this third treatment with pep- 

 sin and acid. The substance was thereupon filtered from the acid 



