80 R. H. Chittenden — Caseoses, Casein Dyspeptone, 



Digestion A. 



Nearly 2 kilos, of moist casein were warmed at 40° C. for a 

 little more than two days, with 10 litres of 0*4 per cent, hydro- 

 chloric acid containing sufficient of the pepsin mixture to insure vig- 

 orous action. After partial neutralization of the acid, the clear fluid 

 was filtered from the semi-gelatinous dyspeptone, made exactly neu- 

 tral with sodium hydroxide and then evaporated until moderately 

 concentrated. On filtering the concentrated fluid through paper, a 

 small residue remained, somewhat gummy, insoluble in dilute acid, 

 but readily soluble in dilute sodium carbonate, from which it was 

 precipitated by either hydrochloric or acetic acid. The amount was 

 too small for study, but it seemed to resemble in reactions casein 

 dyspeptone. 



The neutral fluid containing the caseoses gave no precipitate 

 whatever on addition of 0*4 per cent, hydrochloric acid or even 

 stronger acid, and in this respect differs from the earlier diges- 

 tions in which the ferment action was continued for a short time 

 only. With dilute acetic acid, however, a slight turbidity was pro- 

 duced, the amount of which was too small to admit of any study of 

 its character. 



The caseoses were precipitated collectively in the form of a heavy 

 gummy precipitate, by saturation of the neutral fluid with ammo- 

 nium sulphate. On boiling the filtrate from this ammonium sulphate 

 precipitate, a small quantity of a second gummy precipitate was 

 obtained. In the filtrate from this second precipitate, no trace of a 

 peptone-like body could be discovered by any of the ordinary tests. 

 Apparently only caseose bodies had been formed. 



The first and main ammonium sulphate precipitate, after being 

 washed by trituration with a saturated solution of ammonium sul- 

 phate, was dissolved in water and the perfectly neutral fluid satu- 

 rated in the cold with sodium chloride. By this means a heavy 

 gummy precipitate was formed, which after being washed with a 

 saturated solution of sodium chloride was redissolved in water, and 

 reprecipitated by saturation of the neutral fluid with salt. After 

 three or four reprecipitations, the protocaseose was considered suffi- 

 ciently pure. 



In this digestion, there appeared to be present more heterocaseose 

 and dyscaseose than in our former experiments, as was evidenced by 

 the small insoluble residues remaining each time the precipitated 

 protocaseose was redissolved in water. These residues of hetero- and 



