372 Prof. J. A. MacWilliam. [Mar. 1 '.., 



And vegetable globulin obtained from flour (by extracting with 

 10 per cent, salt solution) behaves similarly. 



D. Fibrin. 



Solutions of fibrin, both when a dilute alkali and when 10 per cent, 

 salt solution are used as the solvents, give white precipitates %vith 

 salicyl-sulphonic acid. 



In the case of all the foregoing proteids (A, B, C, and D) the 

 precipitate does not redissolve on heating ; on the other hand it 

 becomes markedly flocculent. 



E. Proteoses. 





Primary albumoses (proto-albumose and hetero-albnraose) were 

 prepared from Witte's peptone by precipitating them with sodic chlor- 

 ide and (after washing with saturated solution of salt) redissolving the 

 precipitate (containing some salt) by the addition of water. The 

 solution so obtained gave a marked precipitate with salicyl-sulpho 

 acid ; but in this case the precipitate redissolved on heating 

 reappeared on cooling. 



Solutions of secondary albumose (deutero-albumose) gave simi 

 results. 



F. Peptone. 



Solutions of peptone were obtained from albumin artificially 

 digested with pepsin and hydrochloric acid, by saturation with am- 

 monium sulphate and subsequent filtration. The filtrate contained 

 peptone; it gave no precipitate with nitric acid, while it gave the 

 xantho-proteic and the biuret reactions. 



On adding a drop of salicyl-sulphonic acid to a small amount of 

 the solution containing peptone, a precipitate was at once formed. 

 This, like the precipitate of albumoses, readily disappeared on heating 

 and reappeared on cooling. 



Solutions containing peptone were also prepared by saturating the 

 artificially digested albumin solution with sodio-magnesic sulphate, 

 and similar results were obtained. 



Solutions of Witte's peptone were (after being faintly acidulated 

 with acetic acid) saturated with ammonium sulphate in some cases, 

 and with sodio-magnesic sulphate in others. The filtrate contained 

 peptone, the other proteids having been precipitated by saturation 

 with the salts named and removed by filtration. The peptone solu- 

 tion yielded, on being tested with saturated solution of salicyl- 

 sulphonic acid, a reaction similar to that described above, a precipi- 

 tate which disappears on heating and reappears on cooling. 



