35 
1889-90.] Dr G. E. C. Wood on Enzyme Action . 
presence of oxygen — under conditions of anaerobiosis — appear then 
to lose their enzyme function, inasmuch as they then cease to 
liquefy the gelatine. As great inconvenience results in many 
investigations from the liquefying colonies destroying the gelatine 
plates before the other, more slowly-growing organisms, have had 
time to develop, Chantemesse and Widal * have attempted, by 
the addition of some substance to the medium, to hold the peptonis- 
ing power temporarily in check. To facilitate the discovery of 
typhoid fever bacilli in the presence of other organisms, as in 
suspected earth and water, they recommended the addition of 
carbolic acid to the gelatine. Control experiments carried out by 
me at the request of Professor Hueppe,f indicated that the 
quantity required to effect this in different species of bacteria varied 
from OOl per cent, to 0T per cent, carbolic acid, and that the higher 
concentrations necessary for the more refractory, entirely prevented 
the development of more sensitive organisms. Other substances were 
accordingly investigated for the purpose of selecting one which, 
while retarding the liquefaction of the gelatine, would still exert no 
injurious action on the microbes. Of those experimented with, 
glycerine seemed most suitable for general use, although the influence 
which it exerted upon this function varied greatly in different 
organisms. This is explained by the fact, that its action appears to 
consist not in operating directly upon the enzymes, but rather in 
offering the microbe a substance as pabulum, which it selects in 
preference to the gelatine. It has been already mentioned that 
Brunton and Macfadyen found that an organism produced a pepton- 
ising ferment when grown on albumen, but a diastatic ferment on 
starch, so that these would appear to be produced according to the 
special temporary requirements of the organism. I had previously 
observed that all the members of the cholera group, when inoculated 
on blood serum, produced sulphuretted hydrogen, and at the same 
time liquefied the medium. If, however, glycerine is added to the 
blood serum the liquefaction and production of sulphuretted hydro- 
gen appear much later, which is, I think, to be attributed to the 
organism obtaining the energy which it required, first from the 
more easily decomposed carbohydrate, and, only when this had 
* Gazette Hebdomadaire, 1887, page 146. 
t Die Methoden der Bakterien-Forschung, page 299, 1888. 
