v PEPTONES AND AMINO- ACIDS 197 



If such were the case, then more than half of the COOH-groupings 

 would be required for this purpose, and so lose their power of com- 

 bining with alkali. Accordingly, the neutralising power of proteids 

 should be less than half as great as that of their hydrolytic decom- 

 position-products." Vernon's results may be explained on the legiti- 

 mate assumption that the products of digestion form salt-like combina- 

 tions. See Chapter VI. (The author.) 



III. PRODUCTS FORMED BY OTHER PROTEOLYTIC ENZYMES 



A ferment occurs in the kidney which, according to Dakin l gives the 

 end-products: ammonia, alanin,a-amino-iso-valerianicacid,leucin, prolin, 

 j)henylalanin, tyrosin, lysin, histidin, cystin, hypoxanthine, indol-deriva- 

 tives, and an insoluble residue of para-nuclein. Arginin and asparctic 

 acid were only feebly represented. Otherwise the ferment resembles 

 trypsin in its action. It acts in an acid medium, and is a typical 

 example of an autolytic ferment. Arginase is discussed on p. 111. 



Erepsiri 2 is found in the animal organism, in addition to pepsin 

 and trypsin. It dissociates albumoses and peptones into amino-acids, 

 but it has no action on natural albumins except on casein. It destroys 

 the biuret-reaction of anti-peptone, but whether it also dissociates the 

 polypeptid not attacked by trypsin has not yet been determined. 



Vernon has shown that erepsin is widely distributed throughout 

 the whole animal kingdom. It occurs in every organ so far investi- 

 gated ; the tissues of mammals are, as a rule, richer in ferment than 

 are those of the pigeon, and warm-blooded animals contain distinctly 

 more erepsin than do cold-blooded ones. Of individual tissues the 

 kidney was even richer in ferment than the intestinal mucous membrane. 

 Next in order to these two tissues came the pancreas, spleen, and liver; 

 then with a considerable drop came heart muscle, whilst skeletal 

 muscle and brain tissue were poorest of all in ferment. Erepsin of 

 mammalian tissue digests peptone about three times less rapidly in 

 neutral than in alkaline solutions, while in acid solutions the digestion 

 rate was thirty to seventy times slower than in alkaline solutions. 

 The various tissue erepsins seem further to be to some extent specific. 3 



Autolytic ferments have been demonstrated by Salkowski, 4 



1 H. D. Dakin, Journ. of Physiol. 30. 84 (1903). 



2 0. Cohnheim, Zeitschr. f. physiol. CJiem. 33. 451 (1901), 35. 134 (1902), 36. 

 13 (1902); S. S. Salaskin, ibid. 35. 419 (1902); F. Kutscher and J. Seemann, ibid. 

 35, 432 (1902) ; J. H. Hamburger and J. Hekma, Koninkl. Akad. van Wetenschapen 

 te Amsterdam, 1902, p. 733 ; H. M. Vernon, Journ. of Physiol. 32. 33 (1904). 



3 H. M. Vernon, ibid. 32. 33 (1904). 



4 E. Salkowski, Zeitschr. f. klin. Med. 17. Suppl. p. 77 (1891) ; H. Schwiening 

 Medizin. Dissertation, Berlin, 1893. 



