80 PHYSIOLOGY OF ALIMENTATION. 



the catalyzers do not appear in the end-products, and may, 

 when the reaction has been brought to a standstill, be recov- 

 ered in an unaltered state. As is well known, the decompo- 

 sition of potassium chlorate and the oxidation of sulphurous 

 acid occur even when the catalytic agents are not present, 

 but much more slowly. 



Any of the ferments may be cited as examples of organic 

 catalyzers. We may mention here lipase, which hastens the 

 chemical decomposition of fat into fatty acid and alcohol, 

 and proteinase, which accelerates the rate of decomposition 

 of proteins into simpler substances. Here also we deal with 

 chemical reactions which take place even when no ferments 

 are present. Under such circumstances the decompositions 

 occur very slowly, however, requiring weeks, months, or 

 years to attain the degree of decomposition which in the 

 presence of the respective ferments may be reached in a 

 few hours. As was found to be the case with inorganic 

 catalyzers, so here also we find that the ferments do not 

 appear in the end-products of the reactions which they 

 catalyze. 



Examples of negative catalyzers are much more difficult 

 to discover. Only isolated ones have been described, and 

 since nearly all of them seem now to be regarded as inhibitors 

 of positive catalyzers, they will not be discussed here. Nega- 

 tive organic catalyzers are entirely unknown, unless we look 

 upon the antiferments as belonging to this group. Whether 

 they do or not must be left undecided until the mode of action 

 of the antiferments has been discovered. These substances 

 decrease markedly the velocity of certain chemical reactions 

 occurring in the presence of a ferment. Until we know whether 

 the antiferment produces its effects by combining with the 

 ferment (either chemically or mechanically) or by decreasing 

 directly the velocity of the chemical reaction, the classifica- 

 tion cannot be made. Only in case the latter of these two 

 possibilities were proved to be the correct one could we 

 look upon the antiferments as negative catalyzers. 



