340 Journal of Agriculture. [8 June, 1907. 



but even granting that all the solid matter were enzyme the amount of 

 change which it can produce is surprising. Thus one part by weight 

 of rennin can transform 100,000 times its weight of caseinogen into 

 casein. 



7. As enzymes accelerate changes, which normally occur but slowly, 

 it can be shown that all these changes are from a condition of a higher 

 to a lower potential energy. The enzyme does not put work into the 

 system that it acts on ; on the contrary it liberates available energy and 

 allows work to be done. The transformation of sugar into alcohol and 

 carbon dioxide is accompanied by the formation of heat ; we may liken 

 the sugar to a reservoir of water on a hill side and the action of the 

 enzyme zymase to the opening of a tap which allows the water to run 

 down into another reservoir at a lower level. The action of an oxidising 

 enzyme which transforms alcohol into water and carbon dioxide we can 

 further liken to a second tap which allows the water in this lower reservoir 

 to rush down to the sea. 



Enzymes are found wherever there is living bioplasm and withov 

 enzymes life is impossible. In most cases, if not all, a number of 

 enzymes working instantaneously or in succession mav be observed. Thus 

 the yeast plant, if placed in a cane sugar solution, can make no use of 

 its zymase unless the cane sugar is first of all split up by another enzyme 

 called inveriase. In the same manner the yeast plant produces maltase 

 which transforms maltose into dextrose and allows the zymase scope for 

 its activity. But most of the veasts employed have no enzyme which can 

 accelerate a change of lactose into dextrose and galactose and hence in 

 a solution of this sugar no alcohol may be produced. 



In many cases we can show that the free enzyme does not exist as 

 such in the cell ; it is present in an inactive form, a mother substance 

 or fro-cuzvnic which we may liken to a knife in a sheath or a gun at 

 half cock. Probably this is the case with all enzymes. 



We see that living bioplasm does not merely store bodies at hiij;h 

 potential energy and let them degrade into bodies of low potential 

 energy ; it can accelerate this degradation and for all we know may be 

 able to check it at the right time and in the required direction. To make 

 a very rough analogy the molecules of food may be likened to a number 

 of wound-up watch-springs, whilst the cell is composed of a number of 

 complicated clockwork mechanisms. Tlie fell then places each spring 

 in the proper machine and sets it going or checks its action when changes 

 in the environment induce it to do so. Only a limited number of springs 

 can be employed, namely those that fit the various mechanisms. 



We find enzymes not only in the food canal where thev are of service 

 in digesting food ; in the tissues for the liberation of energy, the getting 

 rid of waste and the formation of new compounds ; but also in every 

 living cell where they have the power of digesting and destro\ ing the 

 cell should the latter be cut off from the circulation. If an organ, say 

 the liver, the spleen or a piece of muscle, be cut out of a living animal 

 or one recently dead, it will begin to disintegrate and its proteins be 

 changed into amino-acids even though bacteria be rigidlv excluded. Thi : 

 process has been termed autolysis or self digestion. If the organ were 

 heated to boiling point then no autolysis would occur and the proteins 

 present would remain intact for many years. Autolysis explains the 

 softening of meat when it is hung and is of immense importance in the 

 digestion of food by horses and ruminants. We see nutolvsis also in 



