PROTEOSES AND PEPTONES. 129 



We formerly designated as peptones those protein bodies which are 

 readily soluble in water and which are not coagulated by heat, whose 

 solutions are precipitated neither by nitric acid, nor by acetic acid and 

 potassium ferrocyanide, nor by NaCl and acid. 



The reactions and properties which the proteoses and peptones have 

 in common were formerly considered as the following: They all 

 give the color reactions of the proteins, but with the biuret test they give 

 a more beautiful red color than the ordinary proteins. They are pre- 

 cipitated by ammoniacal lead acetate, by mercuric chloride, tannic, phos- 

 photungstic, and phosphomolybdic acids, by potassium-mercuric iodide 

 and hydrochloric acid, and also by picric acid. They are precipitated 

 but not coagulated by alcohol, that is, the precipitate obtained is soluble 

 in water even after being in contact with alcohol for a long time. The 

 proteoses and peptones also have a greater diffusive power than native 

 proteins, and the diffusive power is greater the nearer the questionable 

 substance stands to the final product, the now so-called true peptone. 



These old views have gradually undergone an essential change. After 

 HEYNSIUS' 1 observation that ammonium sulphate was a general pre- 

 cipitant for proteins, and for peptones in the old sense, KUHNE and his 

 pupils 2 proposed this salt as a means of separating proteoses and pep- 

 tones. Those products of digestion which separate on saturating their 

 solution with ammonium sulphate, or can indeed be salted out at all, 

 are considered, by KUHNE and also by most of the modern investigators, 

 as proteoses, while those which remain in solution are called peptones 

 or true peptones. These true peptones are formed in relatively large 

 amounts in pancreatic digestion, while in pepsin digestion they are formed 

 only in small quantities or after prolonged digestion. 



According to SCHUTZENBERGER and KUHNE 3 the proteins yielded 

 two chief groups of new protein bodies when decomposed by dilute 

 mineral acids or with proteolytic enzymes; of these the anti group shows 

 a greater resistance to further action of the acid and enzyme than the 

 other namely, the hemi group. These two groups are, according to 

 KUHNE, united in the different proteoses, even though in various relative 

 amounts, and each proteose contains the anti as well as the hemi group. 

 The same is true for the peptone obtained in pepsin digestion, hence he 

 calls it amphopeptone. In tryptic digestion a cleavage of the ampho- 



1 Pfliiger's Archiv, 34. 



2 See Kiihne, Verhandl. d. naturhistor. Vereins zu Heidelberg (N. F.), 3; J. Wenz, 

 Zeitschr. f. Biologie, 22; Kiihne and Chittenden, Zeitschr. f. Biologic, 22; R. Neu- 

 meister, ibid., 23; Kiihne, ibid., 29. 



3 Schiitzenberger, Bull, de la Soc. chimique de Paris, 23; Kiihne, Verhandl. d. 

 naturhist. Vereins zu Heidelberg (N. F.), 1, and Ktthne and Chittenden, Zeitschr. f. 

 Biologie, 19. See also Paal, Ber. d. deutsch. chem. Gesellsch., 27. 



