DEFENSIVE FERMENTS OF THE ANIMAL ORGANISM 21 



other substances than those essential to the reaction. 

 It is a well-known fact that the slightest contamina- 

 tion may influence the reaction to a very great extent. 

 It may either fail altogether, or be retarded, or may 

 even be diverted into quite a different direction. 

 We meet with great difficulties if we have to follow 

 up several reactions in one and the same medium. 

 Intermediate products mav act, one upon the other, to 

 such an extent that we arrive at a series of final pro- 

 ducts whose origin it would be extremely difficult to 

 account for. Now, if in an animal organism the 

 separate processes were not regulated in a very strict 

 manner, and if, for instance, the blood did not receive 

 substances which are in harmony with it, that is, 

 always transformed in a definite and regular manner, 

 it would be difficult for us to understand how 

 the separate secretions always attain their aims 

 in a very certain way, and how they are able 

 locally to attack particular metabolisms, and either 

 retard, or hasten, or initiate them. 



There is not the slightest doubt that the course of 

 this metabolism, as well as the inter-relations of the 

 cells of a particular organ, is only imaginable under 

 the supposition that the metabolism of the whole 

 organism is regulated in the most precise way, not 

 only quantitatively, but also qualitatively. We are 

 bound to imagine that, in the work of the cells, the 

 same stages of decomposition recur regularly, and 



