OF PUTREFACTION AND OTHER FERMENTATIVE CHANGES. 321 
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. fermenta- 
tive change occurred. Nor is the fact less significant in its bearmg 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 tem- 
peratures of evolution 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 torule, 
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 perfectly 
free from organisms by merely applying an efficient antiseptic as a preliminary 
measure to the meatus urinarius; and I have before referred to the high interest 
which attaches to this point. 
Secondly, it shewed that if an organic liquid is obtained in an uncontami- 
nated state to begin with in a “heated” wine-glass, covered with a “heated” 
cap shaped like an evaporating dish, and further protected by a glass shade, 
we are secure against the introduction of any organism from without, so long 
as the arrangement is left undisturbed. 
Further, the permanent freedom from contamination in this glass was parti- 
cularly satisfactory, because, seven days after it was charged, I had removed 
a drachm of the liquid from it by means of a “heated” pipette, in order to 
ascertain the effect of water upon the unboiled urine as above .alluded to (see 
p. 310). If no organic development resulted from the sudden entrance of so 
considerable a volume of air as then passed into the glass to teke the place of 
the liquid withdrawn, it follows that, various as are the organisms which 
float in the atmosphere, they constitute but a very small proportion of the 
* Tt may be urged that the particles of dust which give rise alike to the development of organisins 
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 shewn 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 con- 
tains 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 aii this liquid donate from 
the same source, but also when it was obtained by the same method from two other individuals. 
VOL. XXVII. PART IL 4P 
