4G PBOTEIDS. 



substances to the ammonium salt, Kiilme and Chittenden have 

 prepared what they regard as the true pure peptones as follows. 1 

 The products of a digestion are neutralised, filtered, very faintly 

 acidulated with acetic acid and saturated with the ammonium 

 salt. The filtrate from the precipitate thus obtained is largely 

 freed from the excess of salt by careful concentration on a water- 

 bath. The ammonium salt is then got rid of by the addition of 

 baryta water and barium carbonate in slight excess, and after 

 filtration these reagents are finally removed by the careful addi- 

 tion of dilute sulphuric acid. The peptone thus obtained may be 

 still further purified by precipitation with phosphotungstic acid. 2 

 The pure peptones thus prepared are strikingly non-precipitable 

 by many of the reagents by which other proteids may be precipi- 

 tated, more especially by ferrocyauide of potassium in presence 

 of acetic acid, a reagent by which practically all other proteids 

 in solution are precipitated. No quantitative statements have as 

 yet been made as to their rotatory power or diffusibility. They 

 are stated to have such an affinity for water that a small portion 

 of the dry substance when moistened with water exhibits the 

 same phenomena as does phosphoric anhydride under similar con- 

 ditions. They also yield an intense ' biuret ' reaction with caustic 

 soda and sulphate of copper. 



Antipeptone may be obtained by the action of either pepsin or 

 trypsin on antialbumose, or by the action of trypsin 011 antialbumate 

 or antialbumid. When purified no leucin or tyrosin can be obtained 

 by the most prolonged action of trypsin oil this peptone. 



Hemipeptone is best obtained by the action of pepsin on hemi- 

 albumose. When purified and digested with trypsin it yields much 

 leucin and tyrosin, and in this respect alone does it differ from 

 antipeptone. 



Amphopeptone. This is the mixture of anti- and hemi-peptone re- 

 sulting from the action of pepsin on proteids. 



Notwithstanding the probable formation of peptones in large 

 quantities in the stomach and intestine, to judge from the results 

 of artificial digestion, a very small quantity only can be found in 

 the contents of these organs. 3 They are probably absorbed as 

 soon as formed. Another point of interest is their reconversion into 

 other forms of proteids, since this must occur to a great extent in 

 the body. We are however as yet ignorant of the manner in which 

 this reverse change is effected. 



It is now generally considered that the peptones are products 

 of the hydrolytic decomposition of the proteids from which they 

 are formed. This view is based partly upon general considera- 

 tions as to the probable nature of the change, from observations 



1 Zt. f. Biol. Bd. xxii. (1886), S 423. 



2 Hirschler, Zt. f. physiol. Chem. Bd. xi. (1887), S. 28. Otto, Ibid. Bd. vin. 

 (1883), S. 136. 



3 Schmidt-Mulheim, Arch. f. Phi/siol. 1879, S. 39. 



