APP.] CHEMICAL BASIS OF THE ANIMAL BODY. 717 



Notwithstanding their probable formation 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 

 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. 



Production. All proteids, with the exception of lardacein (see p. 720), 

 yield peptones (and other products) on treatment with acid gastric or 

 alkaline pancreatic juice, most readily at the temperature of the human 

 body. Peptones are likewise produced, in the absence of pepsin and 

 trypsin, by the action of dilute and moderately strong acids at medium 

 temperatures, also by the action of distilled water at high temperatures 

 under pressure. For various methods of preparing peptones, see Haly l 

 Aclamkiewicz 2 , Henninger 3 , and Pekelharing 4 . 



It appears possible to reobtain ordinary coagulable proteids from peptones by 

 the action of either prolonged heating to 140 170 C. or of dehydrating agents 5 . 



No difference in percentage composition between peptones and the 

 proteid from which they are formed has, at present, been definitely 

 established. 



We have used the phrase 'peptones' in the plural number because 

 we have reason to think that more than one kind of peptone exists. 

 Meissner 6 described three peptones, naming them respectively A- B- 

 and C-peptone. He distinguished them as follows. A-peptone is 

 precipitated from its aqueous solutions by concentrated nitric acid, and 

 also by potassic ferrocyanide in the presence of even Aveak acetic 

 acid. B-peptone is not precipitated by concentrated nitric acid, nor 

 will potassic ferrocyanide give a precipitate unless a considerable 

 quantity of strong acetic acid be added at the same time. C-peptone is 

 precipitated neither by nitric acid nor by potassic ferrocyanide and 

 acetic acid, whatever be the strength of the acetic acid. In place how- 

 ever of speaking of all' these as peptones, it is better to consider C- 

 peptone as the only real peptone, and the A- and B-peptones as not 

 peptones at all. Nevertheless we have reason, from the researches of 

 Kiilme, to speak of more than one peptone, viz. of a hemipeptone which 

 is capable under the action of trypsin of being converted into leucin and 

 tyrosin, and of an antipeptone which resists such a decomposition. The 

 name antipeptone is given to the latter on account of this resistance which 



1 Pfliiger's Arch. Bd. ix. (1874) S. 585. 



2 Die Natur u. Ndhrwerth d. Ptptons (1877), S. 33. 



3 De la Nature et du Role physiologique des Peptones, Paris, 1878. 

 PflUger's Arch., Bd. xxn. (1882), S. 185. 



5 Henninger, loc. cit., Hofmeister, Zeitsch.f.physioL Chem., Bd. n. (1878), S. 206. 

 Pekelharing, loc. cit. 



6 Zeitschr. f. rat. J/7., Bde. vii., YIII., x., xii. und xiv. 



