and Casein Peptone. 87 



reaction with cupric sulphate, but the striking differences in composi- 

 tion and reactions between the purified sodium cliloride precipitate 

 and the acetic acid precipitate (when freed from acid) point to a 

 totally different nature, and we are inclined to consider the latter as 

 a deutero body, probably contaminated with a little protocaseose, 

 and for convenience we propose to call it a deuterocaseose. 



It is unquestionably very difficult, if not almost impossible, to isolate 

 the individual caseoses in a state of perfect purity. Whenever one 

 is precipitated, it usually brings down with it more or less of any 

 other caseose present and such admixtures are very hard to remove. 

 It is, we think, owing to this fact that we have not been able to 

 obtain a deuterocaseose sufficiently free from protocaseose as not to 

 give any precipitate on saturation with sodium chloride. 



That form of caseose in this digestion which was not precipitated 

 by salt, or by salt and acetic acid, but which appeared on addition of 

 ammonium sulphate in the cold, is probably a mixture of a deutero and 

 and what we term (3 deuterocaseose, with possibly an intermediate 

 body. 



The name (3 deuterocaseose, we apply to that caseose not readily 

 precipitable by saturation with ammonium sulphate in the cold, and 

 which is generally found in a greater or less quantity in the filtrate 

 from the precipitate produced by saturation with ammonium sulphate. 

 It is precipitated fairly pure, as a sticky gum, by simply boiling the 

 saturated ammonium sulphate filtrate and is especially characterized 

 by its low content of carbon, and by its non-precipitation with acetic 

 acid and potassium ferrocyanide, with nitric acid, and with cupric sul- 

 phate. It stands, unquestionably, nearer to peptone than a deu- 

 terocaseose and is doubtless formed from the latter by the continued 

 action of the ferment. 



Digestion B. 



In this digestion, 2 kilos, of moist casein were warmed at 40° C. 

 for eight days, with about 5 litres of 0*4 per cent, hydrochloric acid 

 containing an active pepsin solution, after which the mixture was 

 partially neutralized with sodium carbonate and filtered from the 

 dyspeptone. The clear fluid was then made exactly neutral (no neu- 

 tralization precipitate) and concentrated to a thin syrup. When cold, 

 proto and heterocaseose were directly precipitated by satm-ation 

 of the solution with salt. Protocaseose was purified by repeated 

 precipitation with salt, etc., as described under A. In this process, 

 the same insoluble residues of hetero and dyscaseose were met witii 



