JR. H. Chittenden — Papoid-digestion. 299 



solved by salt solution, dilute acid or alkali, is composed mainly of 

 insoluble or coagulated proteid. 



The addition of distilled water to a clear, aqueous solution of 

 papoid produces a pronounced turbidity, which disappears at once 

 on the addition of a little salt solution, thus showing the presence 

 of a globulin which is obviously held in solution by virtue of the 

 salts contained in the preparation. 



Concentrated hydrochloric acid added to a clear, aqueous solution 

 of papoid gives a heavy white precipitate of proteid matter, readily 

 soluble in excess of the strong acid. 



Concentrated nitric acid, under similar circumstances, produces a 

 heavy white precipitate, which on heating or boiling dissolves in 

 great part, yielding a reddish-yellow solution. On cooling this 

 solution, the precipitate reappears, dissolving again as the mixture 

 is heated, and once more reappearing as the fluid cools. This reac- 

 tion is due to the presence of an albumose, while the accompanying 

 body precipitated by nitric acid, but insoluble on heating, is a 

 globulin, presumably the same as that previously noted in the in- 

 soluble* matter. 



Acetic acid and potassium ferrocyanide produce a heavy white 

 precipitate only in part dissolved by warming. 



Boiling a clear, aqueous solution of papoid gives rise to a tur- 

 bidity, which on prolonged boiling passes into a flocculent precipi- 

 tate. This precipitate is insoluble in 0*2 per cent, hydrochloric acid, 

 and is therefore presumably composed of coagulated globulin. 



Addition of magnesium sulphate in substance to an aqueous solu- 

 tion of papoid precipitates the globulin present, with perhaps some 

 albumose. At first sight, from the milky appearance of the fluid, 

 the precipitate appears quite voluminous, but the amount is in 

 reality not large. On adding crystals of sodium sulphate to the 

 filtrate from the above precipitate, in such quantity as to insure 

 complete saturation of the fluid and with formation of sodio- 

 magnesium sulphate, a second heavier precipitate is produced, com- 

 posed mainly of albumoses (one or more) which agglutinates into a 

 somewhat gummy mass, especially on the addition of a drop or two 

 of acetic acid. With this precipitate of albumose, the proteolytic 

 ferment appears to be mainly associated. 



In the filtrate from this second or sodio-magnesium sulphate pre- 

 cipitate, the presence of peptone, in considerable quantity, can be 

 shown by the biuret test. Or, by directly saturating an aqueous 

 solution of papoid with ammonium sulphate while warm, the albu- 



