M. H. Hoffmann on Fermentation. £77 



placed in a narrow-necked bottle and left unstopped, its surface 

 is covered in a few days with tufts of Mucedinea, 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 



