AND ITS BEARINGS ON PATHOLOGY 381 
The lactic fermentation, then, resembles the alcoholic in being a typical 
catalytic fermentation, the milk-sugar being broken up into lactic acid without 
loss or gain of atoms, while the simultaneous appearance of another product in 
small quantity presents another feature of similarity. A further point of 
apparent analogy between these two fermentations has been brought out by 
the investigation which forms the subject of this communication. In the 
experiment of inoculating ten glasses of pure boiled milk with drops calculated 
each to contain on the average a single Bacterium lactis * five of the glasses 
were capped liqueur-glasses such as have been above described, but the other 
five were in the form of test-tubes with suitable caps, employed in order 
that I might be able to transport them to London without spilling the milk. 
The milk was in about the same quantity in the two sets of vessels; but the 
test-tubes being narrower than the liqueur-glasses, the contained milk in the 
former had about twice the depth and a considerably smaller free surface, 
affording much less opportunity for the access of the atmosphere to the milk. 
The result was a very marked difference in the times of coagulation of the milk 
in the two sets of glasses; that in the test-tubes, where clotting took place at 
all, being solid within three and a half days of the time of inoculation ; whereas 
the milk remained fluid in all the liqueur-glasses till about twelve hours later, 
and in some of those glasses which ultimately curdled the change did not occur 
till nearly twenty-four hours after it had taken place in the test-tubes. Or in 
other words, assuming that the curdling of the milk implied the formation of 
a certain amount of lactic acid, it appeared that the more free exposure to the 
air in the liqueur-glasses had exercised a retarding influence upon the lactic 
fermentation in them. The facts, therefore, reminded me of Pasteur’s observa- 
tions as to the effect of atmospheric exposure in checking the alcoholic fermenta- 
tion. In the time that has passed between the delivery of this communication 
and its publication I have made an attempt to verify the observation, and also 
to ascertain whether the analogy with the corresponding fact in the alcoholic 
fermentation was real or only apparent. Tor oxygen might be conceived to retard 
the lactic fermentation in either of two ways : either on the same principle as in 
the alcoholic fermentation, by supplying an element necessary for the nutrition 
of the organism, and so preventing the operation of its deoxidizing agency, 
with attendant catalysis, or on the totally opposite principle of the free oxygen 
of acting upon sugar in the same manner as emulsin acts upon amygdalin, one of the most beautiful 
examples of pure catalysis known to chemists. Pasteur alludes to this suggestion in his work above 
referred to (Etudes sur la Biére, p. 315) as conceding the point for which Pasteur has always contended, 
viz. that the organism is the primary and essential fermentative agent. And though it seems hardly 
called for in the case of alcoholic fermentation in presence of Pasteur’s facts, yet it seems not at all 
improbable that the principle may be found to apply to some of the catalytic fermentations. 
TESee P1375; 
