364 ON THE LACTIC FERMENTATION 
hour. All these glasses underwent fermentations, and exhibited organisms under 
the microscope, but none showed the lactic fermentation or the Bacterium lactis. 
With regard to the cause of the strange, perhaps unprecedented, appear- 
ances presented by the milk in the little glasses shown to the Society, the explana- 
tion undoubtedly is, not that organisms of a specially rare kind were here present, 
but that species, perhaps exceedingly frequent in other media, had an excep- 
tional opportunity for coming forward in milk, in consequence of the exclusion 
of ferments such as the lactic, the butyric, &c., which, when present in milk, as 
they commonly are, take the precedence of others, and so alter the fluid as to 
render it an unsuitable pabulum for the multitude of other kinds. 
Here I have another set of little test-tube glasses, twelve in number, with 
which the same experiment was repeated two days later, only with still more 
careful precautions against the entrance of organisms from the air or from the 
teat ; but even here, although the appearances are less conspicuous than those 
in the other twenty-four, a careful inspection shows that, in ten out of the twelve, 
organisms of one kind or another have entered, but two of them remained per- 
fectly unchanged in aspect six weeks after the performance of the experiment, 
and on examining the milk from one of these I found it fluid, perfectly natural 
in reaction and in taste, and free from any organisms that could be discovered 
by the microscope. Thus was at length attained the object of these experi- 
ments with the little glasses, viz. the proof that unboiled milk, as coming from 
a healthy cow, like urine from a healthy bladder, really contains no material 
capable of giving rise to any fermentative change or to the development of any 
kind of organism which we have the means of discovering. 
The lactic ferment is as scarce in ordinary water as we have seen it to be 
in the air. If I prepare a series of glasses of boiled milk in the way that has 
been described, and add to each a drop, say half a minim, of tap water, I find 
that fermentative changes, such as putrefactive or butyric alterations, occur in 
all, but that none exhibit the souring or curdling of dairy milk. An extremely 
instructive experiment is to inoculate each of a series, say ten, of such glasses 
with a very small drop of a constant size for all, which can be readily done by 
means of a syringe like this (Fig. 8), having a graduated nut (a), revolving 
on a fine screw on the piston rod (6), each degree on the nut corresponding to 
I—1ooth minim, so that either 1-10oth, or 1-5o0th, or 1—2o0oth, if it be desired, 
can be expelled at pleasure Supposing 1-100th minim of water to be thus 
* It is essential to the precise working of this apparatus that there be nothing elastic in its com- 
position, otherwise drops of varying size will be furnished by it. Thus, an india-rubber junction between 
the syringe and the nozzle is inadmissible. The nozzle of glass tube (c) is screwed upon the body of the 
syringe by means of the brass adapter (d), to which the glass tube is secured with a cement which I have 
found very useful on account of its power of resistance to the action of boiling water, viz. finely powdered 
