244 INACTIVATION OF TRYPSIN. I 



strong acid at about the same pH.^^ This mechanism will evidently 

 lead to the result that the solution containing inhibitor will be rela- 

 tively more active compared to the control solution as the hydrolysis 

 proceeds, which is the experimental fact. The same fact has been 

 noted in immunology in comparing the action of free toxin and of a 

 mixture of partially neutralized toxin. Bordet^^ considers that it is 

 the degree of activity of the total amount of toxin that is affected by 

 the antitoxin and not the concentration of free toxin. His experi- 

 ment is similar to the trypsin experiment just discussed, inasmuch 

 as he found that a small amount of free toxin reacts at first more 

 rapidly than a mixture of toxin-antitoxin, but that as the reaction 

 proceeds, the mixture becomes relatively much more efficient. 

 Bordet's explanation will not explain the results with trypsin quanti- 

 tatively while the assumption of the formation of an inactive com- 

 pound between the trypsin and inhibitor allows all the peculiarities 

 of the reaction to be calculated. It does not follow, of course, that 

 the toxin-antitoxin reaction is the same as the trypsin-inhibitor 

 reaction, but it seems that the same explanation will apply quali- 

 tatively to both. 



^^ If the pH of the solution containing the strong acid is slightly lower than 

 that of the weak acid, the rate of hydrolysis will at first be greater in the solution 

 containing the strong acid. The rate of hydrolysis in this solution will decrease 

 rapidly, however, since the concentration of hydrogen ions will be diminished by 

 the products of hydrolysis — just as is the concentration of free trypsin in the pres- 

 ent experiment. The rate of hydrolysis in the weak acid solution, however, will 

 remain nearly constant since the hydrogen ions which combine with the products 

 formed will be replaced by the dissociation of more of the weak acid. The rate 

 of hydrolysis in the weak acid solution will therefore constantly increase as com- 

 pared to the rate of hydrolysis in the strong acid solution. An example of such 

 an experiment is given in a preceding paper (Northrop, J. H., /. Gen. Physiol., 

 1920-21, iii, 725, Fig. 3. Curves III and IV). 



^^ Bordet, J., Immunite, Paris, 1920. p. 530. 



