CHAP. II.] DIFFUSIBILITY OF PEPTONES. 141 



thymol and and a fragment of purified trypsin, were sufficient to 

 effect the cleavage of the peptone. On concentrating the neutralised 

 solution, and boiling the residue" with alcohol, a residue was obtained, 

 in which, without further preparation, balls of leucin and bundles of 

 crystals of tyrosin were to be seen under the microscope. From the 

 products of such digestion, it was easy to separate tyrosin in a state of 

 purity. Further, a few grams of the same preparation were heated 

 for several days with six times their weight of sulphuric acid (2 parts 

 acid and 3 of water) and after removing the acid with barium 

 hydrate, tyrosin and leucin were found among the decomposition 

 products. 



From antipeptone, subjected to the action of acid, on the other 

 hand, whilst leucin was constantly, tyrosin was only occasionally 

 obtained, and, then, in such traces as to be referable to accidental 

 impurity of the antipeptone used. 



It is impossible, by any process as yet known to 

 Preparation of us to p re p are from ampho-peptone, or from its antece- 

 pure Hemipep- -, r ,1 i -\ 



tone and Anti- c l ents > a perfectly pure hemipeptone, uncontammated 



peptone. by antipeptone. On the other hand, in consequence 



of the destructibility of hemipeptone on digestion with 

 trypsin, antipeptone (tryptone) can be obtained from ampho-peptone 

 uncontaminated by hemipeptone. A fuller description of antipep- 

 tone will be given under the pancreatic enzymes. 



Divisibility Funke 1 pointed out that peptones in aqueous 



of the pep- solution pass through filter paper, and diffuse through 

 tones - animal membranes and through parchment-paper, with 



much greater facility than other proteids. The considerable diffusi- 

 bility through thin animal membranes is undoubted, and contrasts 

 with that of other proteids ; through good parchment-paper, though 

 the diffusion of peptones is much greater than that of other proteids, 

 it is absolutely very small, so that dialysis is employed with great 

 advantage in freeing solutions of peptones from salts, but not to 

 separate peptones from other colloidal bodies, as, for instance, from 

 pepsin. The very sparing diffusibility of peptones through parch- 

 ment-paper was first drawn attention to by v. Wittich 2 , and after- 

 wards confirmed by Maly, Herth, and many others. 



Chemical Composition of the Peptones. 

 The researches of Malv 3 , Herth 4 and Henninger 5 , established 



1 Funke, Lehrbuch d. PhysioL, Vol. I. 5 Aufl. p. 208. 



- v. Wittich, ' Ueber die Diffusibilitat der Peptone.' Berl. klin. Wochenschrift. 

 1872, N. 37. Abstracted in Maly's Jahreslericht, Vol. n. p. 19. See also Hermann's 

 Handbuch, Bd. v. 2. Th. S. 296. 



3 Maly, ' Ueber die chemische Zusammensetzung und physiologische Bedeutung 

 der Peptone.' Pfiviger's Archiv, Vol. ix. (1874), p. 585. 



4 Herth, ' Ueber die chemische Natur des Peptons und sein Verhaltniss zum 

 Eiweiss.' (Aus dem Lab. v. Prof. Maly.) Hoppe-Seyler's Zeitschrift, Vol. i. (1877), 

 p. 277. 



5 Henninger, De la nature et du role physiologique des peptones. Paris, 1878. 



