48 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
less strongly characterized and differentiated from them than they are from one another. 
Whether it be granted or not that the living cell intermediately develops a 
type of energy peculiar to itself, the experimental fact remains that the cell is capable 
of inducing actions of greater complexity and involving more markedly endo-thermic 
reactions than the soluble ferment. 
Thus the reaction induced by the enzyme is of a simple type, either a single 
substance is resolved into two or more substances, or by an inverse change two or 
more simple substances are united to form a single substance ; there are no intercurrent 
reactions of different type involved. But in the case of the cell, several reactions take 
place concurrently, and the energy set free from one reaction is used in running 
another, so that the whole process becomes complex and of a character, as to the 
nature of products formed, which is quite different from that due to an enzyme. 
In one important respect, however, the action of the living cell and the enzyme are 
identical, that is, that neither the living matter of the cell nor the substance of the enzyme 
enters permanently into the chemical reaction induced. The quantities of matter trans- 
posed from one chemical form to another are disproportionately large, compared to the 
masses of cell or enzyme responsible for the chemical change, and hence, both cell and 
enzyme must be regarded essentially as energy-transformers for chemical energy. 
The fact that enzymes are incapable of inducing markedly endo-thermic re- 
actions is due to the fact, insisted upon above, that the reaction is simple in type, and 
hence an enzyme cannot oxidize part of the material, and utilize the supply of energy 
so obtained for the formation, by an inverse process, of a«6ubstance containing more 
chemical energy per unit weight than the original substance. 
An enzyme can, however, under suitable conditions of concentration of the 
solution and temperature, induce synthetic change by altering the level of the equi- 
librium between the various types of energy interacting in the system. 
Such synthetic changes due to enzymes occur, however, only in the case of 
reactions in which there is little change of chemical energy, as shown by the equality 
of heats of formation, within the limits of experimental error, of the substances 
involved in the reaction. 
No synthesis due to enzymic action has been shown to occur where the heat 
of combustion of the substance formed in the synthesis is measurably greater than 
those of the substances from which it is formed. 
All such reactions belong typically to the class of reactions known as reversible 
reactions, and in them the amount of chemical energy involved in the reaction is small 
compared to the masses of the reacting substances, or to the thermal capacities of 
those masses. 
In such reactions the equilibrium point is that stage in the reaction at which 
there is equilibrium between the potential factors of the forms of energy (viz., 
osmotic, thermal, and chemical) involved in the reaction. 
