6 Mendel and Underhill — Papdin-digestion. 



tions in the digestion of various proteids. While nearly all writers 

 have found that weakly alkaline fluids favor the action of papain, 

 there has heen great diversity of experience regarding the influence 

 of acid reaction. 1 Undoubtedly the conditions determining the 

 character of the acid reaction, i. e., the presence or absence of free 

 mineral acid, are of decisive influence and have been overlooked in 

 this connection, as frequently elsewhere, in discussions regarding 

 enzyme activity. 2 Our own experiments confirm the results obtained 

 by the three writers above named in showing pronounced proteo- 

 lytic activity in digestive mixtures with various reactions. 



Methods. The general course of these experiments has been to 

 treat the proteid used with relatively concentrated solutions of the 

 enzyme preparation under examination, enough sodium fluoride 

 being dissolved in the mixture in every case to make the total 

 strength of this antiseptic equivalent to at least one per cent. Pre- 

 vious trials had demonstrated that this salt does not interfere seri- 

 ously with the action of papain. 3 The digestions were carried on in 

 an oven at 37° C. In the series of quantitative trials reported below 

 ten grams of moist coagulated egg-white, finely comminuted, were 

 used. To this, 50 c.c. of 0.2 per cent. HC1 were added for the acid 

 digestions, 50 c.c. of 2 per cent. HNaC0 3 solution for the alkaline 

 digestions, and 50 c.c. of water for the neutral media. Finally 1.5 

 grams of papain were digested with 125 c.c. of water and 50 c.c. 

 of the filtrate were employed in each digestion. Each digestion 

 mixture was thus made up as follows : 



10 grains of moist proteid (2.025 grams of dry proteid), 

 100 c.c. of fluid containing 1 gram NaF. 



/ 0.1 per cent. HC1, or 

 papain and^ 1.0 " HNaC0 3 , or 

 \ water. 



Control trials were simultaneously carried out with boiled papain 

 solutions, and lastly the solvent action of the fluids used was ascer- 

 tained. 4 After allowing the digestive action to proceed at 3T C C. 



1 For the literature references on this point see Oppenheinier : Die Fermente 

 und ilire Wirkungen, 1900, p. 136 ; also Pickardt : Ceutralblatt fur Physiologic 

 1900, xiv, p. 351. 



2 Cf. Hanford : American Journal of Physiology, 1900, iv, p. 250. 



3 Cf. Chittenden, Mendel and McDermott : American Journal of Physiology, 

 1898, i, p. 259. 



4 The complete extent of digestive action is not always accurately represented 

 in this way, since what is estimated as undigested residue may frequently be 

 made up in part of transformation products, like antialbumid. resulting from 

 the work of the enzyine. 



