174 MASS. EXPERIMENT STATION BULLETIN 167. 



On the other hand, in the media where no growth was observed Ph 

 remained practically constant. 



2. Minimum Ph for B. subtilis Ues between 4 and 5. 



3. Optimum Ph for B. subtilis hes between 7.5 and 8.5. 



4. Maximum Ph for B. svhtilis hes between 9 and 10. 



5. The alteration of Ph in the media occurred in such a way that dif- 

 ferent Ph's were brought toward the optimum Ph. This peculiar altera- 

 tion of Ph, or so-caUed "automatic adjustment," is very interesting 

 because it occurred in each of four similar experiments which came under 

 the author's observation. An explanation of this peculiar adjustment 

 remains to be discussed. It was thought by the author that this phenom- 

 enon is due to the production of ammonia present as an end-product of 

 proteolysis. This cannot be true, however, because Ph above the optimum 

 decreased rather than increased; for instance, Ph = 9.43 became Ph = 8.01. 

 Again, it cannot be due to the increased amount of amphoteric substance 

 which has resulted from the growth, because Ph = 8.17 changed only to 

 Ph = 8.13, while other Ph's were altered markedly, and also against theo- 

 retical expectation. It is pertinent to consider the presence of the so- 

 caUed "protective substance" in enzymatic work in connection with this 

 discussion. In enzymatic work it has been shown by Hudson and Paine ^ 

 and others that cane sugar acts as a protective substance in the case of 

 invertin, especially in the destruction of the enzyme by ethyl alcohol. 

 Recently Chapman ^ demonstrated the relative action of propyl alcohol, 

 methyl acetate and methyl-ethyl ketone upon the invertin, with and 

 without sugar, bringing out strikingly the protective value of cane sugar. 

 It may not be erroneous to consider that in this investigation a protective 

 substance is present or produced in the medium, the action of wliich may 

 be analogous to that of cane sugar in the case of invertin; that is, the 

 hydrogen ion concentration in the medium is altered by some protective 

 substances bringing it to the optimum concentration for proteolytic 

 enzymatic activity. 



Determination of Character of the Proteolysis, viz., Ereptic, 

 Peptic and Tryptic in Nature. 



In the media consisting of different hydrogen ion concentrations, 

 namely Ph = 1 to Ph = 13, wliich have been described elsewhere, the 

 character of the proteolysis was determined according to the following 

 general principle : ' if the proteolysis occurs in the media measuring Ph = 7, 

 then it is suggested that this is ereptic ; greater than Ph = 7, tryptic ; and 

 less than Ph = 7, peptic in nature. 



' Jour. Amer. Chem. Soc, V. 32, 1910, 1353. 



2 Internat. Zeitschrift f. Physik.-Chem. Biologie, Bd. I, Heft 5 u. 6, S. 293. 



» Julius Wohlgemuth. Grundriss der Fermentmethoden, 1913, 135, 182; C. Oppenheimer. 

 Die Fermente u. Ihre Wirkungen, Bd. II, 1913, S. 617; Sven Palitzsch u. L. E. Walbum. Biochem. 

 Zeitschr., Bd. 47, Heft 1, S. 1-35. 



