FERMENTS. 467 



Let us, at the start, ascertain what are the characteristics of the ferments 

 themselves. 



The first remarkable fact is that they are never found as end-products 

 of the reactions. They remain unchanged. The smallest amounts 

 suffice to repeat the same reaction a countless number of times. Thus, 

 invertase is capable of inverting at least 200,000 times its own weight of 

 cane-sugar, 1 rennin at least 400,000 parts of casein. 



The action of the ferments should, theoretically, be an unlimited one. 

 There is, however, as has been shown in the case of rennin, 2 a gradual loss 

 of efficiency. This is not, however, caused by the reaction itself. We also 

 know, as we shall see more in detail later, that the ferments have a specific 

 action, i.e., trypsin, for instance, only attacks protein, and never the car- 

 bohydrates or fats; while diastase never acts on albumin, nor does lipase 

 ever have any effect upon carbohydrates or albumins. We know, further- 

 more, that the ferments are produced by living cells, some of them being 

 given up by the cells, while others are retained in the cell itself. Finally, 

 we are, in most cases, acquainted with the end-products, and are thus able 

 to draw conclusions regarding the nature of most reactions which they 

 cause to take place. 



Now there are in inorganic chemistry a great many facts known, which 

 remind us very much of the behavior of ferments. We refer to those 

 chemical processes in which the presence of a minimum amount of a 

 given substance is sufficient to produce a marked acceleration. We 

 speak in such cases of catalyzers, and call the whole process catalysis, or 

 one of contact action. Ostwald 3 defines catalysis as an acceleration of a 

 slow chemical change brought about by the aid of a foreign substance. Accord- 

 ing to this definition, the reaction in question is not started by the cata- 

 lyzer, but whereas it takes place very slowly of itself perhaps even to 

 an imperceptible extent the rate of change is accelerated by the presence 

 of a specific substance. In support of this assumption we have the fact 

 that increasing the amount of the catalyzer causes further acceleration of 

 the catalysis. If the process served merely to start the chemical change, 

 we should hardly expect that the amount of catalyzer present would have 

 any influence, and at all events the speed of the reaction would be inde- 

 pendent of the amount of contact substance present. We shall subse- 

 quently come back to this definition. We are interested here in the simi- 

 larity between these contact substances and the ferments. One of the 

 chief common characteristics is the fact that neither appears among the 



1 J. Chem. Soc. Trans. 57, 834 (1890). 



2 Reichel and Spiro: Hofmeister's Beitrage, 6, 68 (1904), and 7, 479 (1905). 



3 Grundriss der allgemeinen Chemie, 3d ed. (1889), p. 514. Ueber Katalyse. Lecture. 

 Hirzel. Leipzig (1902). Compare also, G. Bredig: Die Elemente der chemischen Kinetik, 

 etc., Ergeb. Physiol. (Asher and Spiro) 1, 134 (1902). 



