AND OTHER FERMENTATIVE CHANGES 283 
in the first instance for forty minutes, and in which, it will be remembered, 
filamentous fungi occurred without either torulae or bacteria—the obvious 
explanation of the difference being that different organisms happened to prevail 
in the air of the rocm at the two periods of exposure. 
The other glass was left permanently covered; aiid the urine in it remained 
permanently free from organic development or putrefactive alteration. After 
the lapse of many weeks, when its bulk had been considerably reduced by 
evaporation, it became turbid, leading me to suspect bacteria. But on apply- 
ing the microscope I found the appearance was occasioned merely by saline 
deposit, and the contents finally dried up into a solid residue, without under- 
going any other perceptible change. 
I need hardly point out how entirely such a fact as this disposes of the 
oxygen theory as regards this particular fluid at ordinary temperatures. Neither 
cover nor shade fitted closely, so that a constant interchange was taking place 
by diffusion between the air in the wine-glass and the oxygen and other gases 
of the external atmosphere ; yet no putrefaction or other fermentative change 
occurred. Nor is the fact less significant in its bearing upon the theories of 
chemical ferments and spontaneous generation. The vesical mucus has been 
commonly regarded as the special chemical ferment of urine: but it was here 
present, unaltered by boiling or any other treatment, yet failing for weeks 
together to produce any fermentative change. And the mere fact that the liquid 
was received into a vessel which had been heated so as to destroy all life within 
it, and afterwards protected from the access of dust, ensured the absence from 
first to last of all organic development. It is, therefore, certain that this urine 
contained no materials or principles capable at ordinary temperatures of evolu- 
tion into living beings. 
At the same time the behaviour of the glasses which were exposed to the 
air in this experiment indicates that the foreign element which gives rise to 
bacteria, like that which occasions the growth of filamentous fungi and torulae, 
may enter in the form of atmospheric dust. 
But the results of this simple experiment were valuable in other respects. 
In the first place, it afforded ample proof that urine may be obtained pertectly 
1 It may be urged that the particles of dust which give rise alike to the development of organisms 
and to- fermentative changes in a fluid like urine are not necessarily organisms, but may possibly be 
little bits of so-called chemical ferments which occasion chemical alterations, that in their turn lead to 
the evolution of organisms by spontaneous generation. Such a view, plausible as it may appear, will 
be shown in the sequel to be utterly destitute of scientific basis. Meanwhile we must be content with 
the sure step mentioned in the text, viz. the fact that neither fresh healthy urine nor its mucus contains 
any such evolutionary particles. I feel justified in stating this as a general truth regarding urine, since 
it has been found to hold not only in numerous other experiments with this liquid derived from the 
same source, but also when it was obtained by the same method from two other individuals. 
