AND OTHER FERMENTATIVE CHANGES 279 
from the first were perfectly clear. I should say that after twenty-four hours 
these glasses, instead of being covered with the glass plate, were put under 
a glass shade common to them all; an exceedingly rude method of experiment- 
ing, merely intended to obtain rough evidence of whether exposure to the air 
would or would not lead to the development of bacteria. Considering, there- 
fore, how imperfect were the means of excluding dust, I was not at all surprised 
to find, in the course of a few days, that the two glasses which had remained 
clear longer than the rest also exhibited organisms of different kinds, into the 
details of which I need not enter further than to say that those of one of the 
glasses included distinct bacteria. 
This experiment, rude as it was, showed clearly that exposure to the air 
might lead to the development of bacteria, provided always that the urine was 
free from contamination to begin with. And, further, the comparative slowness 
of any change in the two glasses which were neither treated with water nor 
intentionally exposed to dust, led me to think that in all probability, if the 
experiment had been performed more rigorously, I should have had no develop- 
ment at all in them; or, in other words, that the method of obtaining uncon- 
taminated urine was really trustworthy. If so, the fact was not only valuable 
as affording a ready means of performing experiments on the question at issue, 
but also exceedingly interesting in itself, as a strong corroboration of the view 
that the healthy living tissues prevent the development of these organisms. 
Accordingly, 1t seemed worth while to perform another similar experiment 
somewhat more rigorously, and this was done on the 21st of November of the 
same year. Wine-glasses were ‘heated’ as before, but each was provided with 
a separate cover, which was also ‘heated’. Two of these covers were inverted 
porcelain evaporating dishes, which had the advantage of preventing the direct 
effect of lateral currents of air; but as [ had only two such dishes at hand, 
I used for the rest of the glasses square pieces of glass plate overlapping well 
in all directions ; anda glass shade was put over allasan additional protection 
from dust. Further, instead of having the urine passed directly into the several 
glasses in succession, which was an inconvenient procedure, I had it introduced, 
in the first instance, into a flask provided with a porcelain cap, the flask having 
been heated over a red fire and allowed to cool under protection of the cap, 
which had also been thoroughly heated. The glasses were then successively 
charged from the flask with as little exposure as possible. The residual urine 
in the flask was boiled for nine minutes, and two additional ‘heated’ and 
covered glasses were charged with the boiled urine, and to one of these a drop 
of tap water was added. I shall speak of those again by and by. As regards 
those charged with the unboiled urine, one was exposed for forty minutes to 
