1889 - 90 .] Dr G. E. C. Wood on Enzyme Action . 
37 
The question now arises, What are the factors which come into opera- 
tion in old cholera cultures, and cause this loss of function 1 It has 
been already stated, that when oxygen is excluded, the organism 
exists without the aid of enzymes. Now, if a culture is left, for 
long, undisturbed, a membrane forms on the surface which effectually 
prevents the entrance of oxygen to organisms which have fallen to 
the bottom of the tube, and the habit of taking its food otherwise 
than by enzymes may perhaps persist for some time after it is again 
grown under ordinary conditions. The most important factor, as 
evidenced by the fact that the age of the culture is essential, is 
undoubtedly the action of the metabolic products of the microbe, 
which accumulate under such circumstances. These products may 
act either as general depressants devitalisingly upon the protoplasm ^ 
as a whole, or specifically upon one or other function. We must in 
this case attribute the action to the presence of some special 
substance, which acts upon this function, as organisms which were 
unaffected by their own products suffered this loss when cultivated 
in sterilised cholera cultures. As the phenols had been found to 
act powerfully in restraining the action of the soluble ferments, 
attention was directed to indol, which Brieger and Salkowski had 
shown to be formed by cholera. The great difficulty and expense 
involved in the preparation of pure indol prevented the experiment 
from being carried out with it, so recourse was had to phenol. The 
method of procedure was as follows : — A series of tubes each con- 
taining 10 c.c. of sterilised bouillon, received quantities, varying from 
1 to 10 drops, of 5 per cent, carbolic acid solution. The organism 
was then seeded in these tubes, and the effect of the varying concen- 
trations investigated. The microbes which were experimented upon 
in this way were Koch’s Cholera bacillus , Micrococcus indicus , Micro- 
coccus prodigiosus , and Bacillus pyocyaneus. These varied greatly 
as regards the quantity required to effect the loss of their enzyme func- 
tion, 1 to 2 drops being sufficient for cholera, while Prodigiosus and 
Indicus required the highest concentrations. Bacillus pyocyaneus 
being still more intractable, showing itself unaffected, even by 10 
drops of carbolic acid, it was finally omitted from the series. The state 
of the enzyme function in the other organisms was tested from time 
to time by inoculation on milk and gelatine. By this means, in 
the space of about six weeks, varieties of cholera, Prodigiosus 
