354 ON THE LACTIC FERMENTATION 
in its present simplified form, has never been published. It is based, in the 
first instance, on the fact which experience has now amply demonstrated, that 
if we have a vessel like this liqueur-glass (A) in a state of purity, covered with 
a pure glass cap (B), the capped liqueur-glass being further covered with a glass 
shade (C), and standing as a matter of convenience on a plate of glass (D), any 
organic liquid contained in the liqueur-glass, provided it be free from living 
organisms at the outset, will remain without any organic development occurring 
in it as long as the arrangement of the glasses is left undisturbed. Or, in other 
words, although an interchange is constantly taking place between the gases 
led 
Nell 
4 ip; ; 
at eB 
FIG. 2. 
of the atmosphere and those in the liqueur-glass—for the cap does not fit at 
all, and the shade is not air-tight—yet the double protection of the glass cap 
and the glass shade effectually prevents access of the atmospheric dust to the 
liquid ; and if the dust is excluded, organisms do not occur in it. 
The glasses are obtained pure by means of heat. I find that exposure to 
a temperature of 300° Fahr. for two hours is sufficient to deprive all living 
material of its vitality. But it is not enough that the glasses should be so 
heated ; it is necessary that the air which enters them during cooling should be 
filtered of its dust. This I secure by heating them in a cast-iron box, the door 
of which (E) is here shown. This door has its circumferential part in the form 
of a groove, capable of being packed with a considerable mass of cotton-wool (F). 
* A curious exception to this general truth was met with by Mr. Godlee in the course of his experi- 
ments made by this method upon the vaccine virus, recorded in the Tvansactions of the Pathological 
Soctety, vol. xxviii. He found that Penicillium glaucum made its appearance in some of his glasses 
in a way that seemed unaccountable, till he discovered that the cupboard in which the vessels were 
kept was infested with acari, and that these creatures crawled up and into the glasses. He further 
found, on examining some of these acari under the microscope, that spores of the Penicillium were to 
be seen actually adhering to their hairs. The wonder now came to be, not that that fungus should 
have entered the glasses, but that other organisms, such as bacteria, should not have been also carried 
in. If there were any reason to apprehend the intrusion of such creatures, they might no doubt be 
easily excluded by placing each glass plate in an ordinary dinner-plate containing glycerine, so as to 
surround the glass plate on all sides with the viscid liquid. 
