476 LECTURE XX. 



The fact that the ferments act asymmetrically leads to the assumption 

 that they themselves are asymmetrically constituted. The ferment must 

 be exactly fitted to act on the compound which is to undergo cleavage. 

 Possibly the assumption, so often made, that the ferment temporarily 

 combines with the substance to be hydrolyzed, will account for the specific 

 behavior of every individual ferment. If this be true, we can easily 

 understand that only a definite ferment can act upon a given compound. 

 This assumption is supported by the observation, that pepsin and papain, 

 for example, form such strong combinations with fibrin that they cannot 

 be removed by washing. It has also been found that the inversion of 

 cane-sugar by ferments is, as a rule, the same during equal intervals 

 of time. 



Further light has been thrown upon this problem by tracing the optical 

 behavior of solutions containing optically-active polypeptides after the 

 addition of a solution containing ferments. 1 -All results indicate that the 

 ferment temporarily unites with the substance which it splits. It is 

 important that the cleavage products tend to prevent the further cleavage 

 of the substance, in accordance with the mass-action law. 



A peculiar significance of the ferments has recently been indicated by 

 certain observations. Morgenroth 2 found that, after subcutaneous 

 injection of rennin in small doses, the serum of the animal so treated, 

 contained a substance which prevented the curdling of milk. This phe- 

 nomenon is analogous to the production of anti-toxin by the animal 

 organism after the injection of a toxin. In one case we obtain an anti- 

 toxin, in the other an anti-rennin. Two per cent of the strongest immu- 

 nizing-serum which Morgenroth obtained, added to milk, prevented its 

 curdling even when the ferment was present to the extent of 1:20,000. 

 Without the addition of anti-rennin, the curdling took place when the 

 ratio was as low as 1 : 3,000,000. Even normal serum is supposed to con- 

 tain some anti-rennin. Such anti-ferments have also been prepared which 

 act against pepsin, trypsin, fibrin-ferment, tyrosinase, lactase, and urease. 

 These experiments are of great importance in two directions if they can be 

 confirmed. In the first place, this discovery will serve to unite a purely 

 biological process with another which, up to the present time, has not 

 been studied by itself. The acquirement of immunity and the formation 

 of anti-ferments may prove to be analogous phenomena; and the toxins, 

 which resemble the ferments in many respects, may belong to the same 

 class of substances. A further analogy lies in the fact that the ferments 



1 Abderhalden and Koelker: Z. physiol. Chem. 51, 294 (1907); Abderhalden and 

 Michaelis: ibid. 52, 326 (1907); Abderhalden and Gigon: ibid. 53, 251 (1907); Abder- 

 halden and Koelker: ibid. 54, 363 (1908). 



2 Zentr. Bact. 26, 349 (1889); 27, 721 (1900). 



