116 THE FERMENTS. 



somewhat higher temperature, by treating with alcohol, or by satu- 

 rating their solutions with neutral salts. 



Mode of Action. The decompositions which the ferments are 

 capable of effecting in suitable media are essentially of a hydrolytic 

 character. This can be readily shown by comparing the decom- 

 position-products to which the ferments give rise with the original 

 substances, when it will be found that, practically without exception, 

 the former contain more water. Nasse, moreover, could demon- 

 strate a distinct increase in the electrical conductivity of watery 

 solutions of starch, for example, when these were treated with dias- 

 tase, showing that dissociated molecules of water must have been 

 present. As to the manner, however, in which these hydrolytic 

 phenomena are brought about we are very much in the dark. On 

 the one hand, we may suppose that the molecular oscillations which 

 take place in the molecules of the ferments are of such a nature 

 as to bring about an increase in the molecular oscillations of the 

 substances upon which the ferments exert their specific activity, and 

 that in consequence of this increase in the oscillations the labile 

 equilibrium of the large albuminous or polysaccharine molecules is 

 disturbed, which in turn would lead to new combinations of atoms 

 to form molecules that are more stable, and the oscillations of which 

 would be more nearly like those of the ferments. According to 

 this theory, then, the action of the ferments would be what has been 

 termed a katalytic action, and analogous to the katalytic action of 

 various metals, such as platinum, gold, silver, etc., which in fine 

 suspension behave in very much the same manner as the ferments 

 (see page 20). On the other hand, we may suppose that the action 

 of the ferments is an action by contact, such that one molecule of 

 the ferment causes hydrolytic decomposition of one molecule of an 

 albuminous substance, for example, and that this decomposition in 

 turn causes decomposition of the adjacent albuminous molecules, and 

 so on. The action of certain ferments, such as the fibrin ferment, 

 and that which causes the coagulation of milk, might very well 

 be explained upon such a basis. For here we see a rapidity of 

 action which scarcely admits of any other explanation ; and direct 

 contact of the ferments with all parts of the surrounding material, 

 moreover, is excluded, as each ferment-molecule must of necessity 

 be at once surrounded by a layer of the coagulated albumin. 



A second class of ferments comprises the oxidizing ferments, 

 which either obtain their oxygen from the air or from decomposed 

 hydrogen peroxide. The first group of these is represented by the 

 oxydases proper, which are active within the cells and tissues as oxy- 

 gen carriers. 



Classification. It has been pointed out that there are no general 

 reactions which are characteristic of all ferments. The ferments 

 can be separated into groups, however, which are fairly well char- 

 acterized by their specific activity and the decomposition-products 

 to which they give rise. They are accordingly divided into the 

 following classes : 



