M. H. Hoffmann on Fermentation. 277 
placed in a narrow-necked bottle and left unstopped, its surface 
is covered in a few days with tufts of Mucedinee, arising from 
the spores which have fallen from the air. Protecting these 
liquids from these spores is the object of the methods of pre- 
servation of Appert and others. The above experiments fur- 
nish a fresh proof that spontaneous generation must be placed 
amongst dreams. 
The following experiment proves that, notwithstanding the 
free action of the air, there is no formation of Infusoria, Fungi, 
or Bacteria when measures have been taken to prevent the 
liquid from containing any germs of these organisms. A 
small alembic is half filled with an organic liquid, and closed 
with a pierced cork, through which is passed a small glass 
tube of one or two lines in diameter, of which the free extre- 
mity is bent down, for one or two inches, in the form of a 
hook ; the liquid is boiled for an hour, the extremity of the tube 
being closed with wadding, which is removed after the liquid 
has become quite cool; the organic matter will then be in free 
and direct communication with the oxygen of the external air, 
and, notwithstanding, it will: remain intact, without any forma- 
tion of Infusoria or Moulds for six months and more, even 
during the hottest summer—evidently because the spores dif- 
fused in the atmosphere cannot penetrate to it. 
Fermentation is therefore only a simple division of the 
groups of organic atoms, which is essentially connected with 
the presence of yeast. M. Hoffmann leaves the question, whe- 
ther the carbonic acid is a secretion of the interior of the yeast- 
cell, or produced by its outer surface, undecided. Vesicles of 
gas are never seen in the interior of one of the active and normal 
cells; nevertheless, carbonic acid might be contained in the in- 
terior in a dissolved state (as in the blood). M. Hoffmann 
says that he does not see how this question can be solved 
directly by experiment. It is certain that the development of 
carbonic acid in a saccharine solution is immediately connected 
with the yeast-cells ; this is proved by the following experiment, 
amongst others :—If a saccharine solution, or freshly prepared 
wort, contained in a test-tube, be divided by a thick plug of 
wadding, and yeast be poured into the upper portion, it is only 
in this that a fermentation will take place, which may be carried 
on until the complete disappearance of the sugar. After the lapse 
of some days, some bubbles of gas pass through the plug of 
wadding, and increase by degrees until they form a stratum of 
gas of 2 to 6 lines in thickness, which completely isolates 
the inferior liquid, but the sugar remains in this without 
alteration. 
“When we see what an energetic and penetrating influence 
