1889 - 90 .] Dr G. E. C. Wood on Enzyme Action. 
45 
view, since Metschnikoff has ascribed the death of microbes in the 
animal body to the mesoderm cells which are able to take np the 
organisms as foreign bodies and digest them. Now, as the organisms 
appear to be unaffected by enzymes,* by general consent the antiseptic 
action of the gastric juice being ascribed entirely to its acidity, even 
assuming that they actually undergo their death in the cells, we 
have no reason to believe that this is due to a process of digestion, 
but rather to some influence exerted by the living protoplasm with 
which it must there come into such close relations. It is probable 
that the struggle which may occur between two microbes in our 
test tube cultivations does not differ essentially in nature 
but only in degree from that which takes place in our body 
between the tissues and the disease germ. In both cases 
the ultimate result of the action and reaction of the cells 
upon each other may turn on the sum of the “conditions of 
existence” to which they are exposed, happening to favour one 
more than the other. Thus when two organisms are sown together 
in a culture fluid, which will “ overgrow ” the other may depend on 
the relative quantity of the two primarily introduced, the nature and 
reaction of the medium, and the temperature at which they are held : 
in a precisely analogous fashion, the growth of a disease germ 
introduced into a susceptible animal and the disease which follows 
is dependent on the quantity introduced (Davaine, Watson-Cheyne), 
the tissue inoculated (Koch, Watson-Cheyne), and it may be the 
temperature at which the animal is kept (Gibier, Metschnikoff, 
Pasteur). It was for long supposed that the products of one 
organism might be highly injurious to another, and that thus the 
sudden disappearance of an organism introduced into a mixture 
might be explained, but more recent experiments tend to ascribe 
much less influence to the products as direct poisons. Kitasato has 
* Organic matter in nature is, in the process known as putrefaction, resolved 
by microbes into its simpler constituents, which in the protoplasm of plants 
are again built up into complex organic bodies. But a part of the organic 
matter undergoing this process is built up into the substance of the microbes. 
These, when dead, appear to undergo a process of disintegration, to be ascribed 
in all probability to the action of their own enzymes, the cellulose ferment 
which Vignal has found to be secreted by “potato-bacilli” exerting its 
action on the cell wall, and the peptonising enzyme upon the albuminoid 
constituents. In this way the constant circulation of organic matter between 
the animal and vegetable kingdoms may proceed without intermission. 
