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study of them has thrown upon the nature of infectious diseases. 
Indeed, the well-known term Zymotic, applied to the large class of 
infectious diseases, points out the analogy which is supposed to 
exist between them and the process of fermentation. And this 
analogy gave rise to the germ theory of disease, a theory the truth 
of which has been confirmed by recent research. In fermentation, 
putrefaction, and disease, the access of the germs of certain micro- 
scopic plants sets up a process of change, the process of which 
is accompanied, nay probably is caused, by enormous growth and 
multiplication of the plant. When fermentation takes place in 
a saccharine solution the greater part of the sugar is re- 
solved into carbonic acid and aleohol, the elements of which, 
taken together, are equal in weight to those of the sugar. A 
small part breaks up into glycerine and succinic acid, and 
one or two per cent. is not yet accounted for, but is, 
perhaps, assimilated hy the Torula plant. The carbonic acid 
escapes in the form of minute bubbles, the alcohol remains in 
the solution, from which it can be separated by distillation. The 
plant by which these chemical changes are connected is the Torula, 
or Saccharomyces Cerevisiz, or yeast fungus. If a small piece of 
germinating yeast is examined under a microscope with a 
magnifying power of 3,000 diameters, it will be seen to consist of 
numerous transparent colourless oval bodies, varying in size 
from ;4; to ;; of an inch (with an average size of =, of an 
inch), some single, but many joined together in heaps or 
strings. Each of these minute bodies is a cell, consisting of a 
thin transparent sac, the ‘ cell wall,’ and its semi-fluid contents, 
the ‘* proto-plasm.”” Under favourable circumstances rapid growth 
and multiplication takes place, minute buds appear on the surface 
of each Torula, which become detached at various stages of their 
rapid growth, some when they are extremely minute, others not 
till they have reached the size of the parent Torula, and have 
themselves developed buds and these yet others. Torule thus 
produced by budding the one from the other frequently continue 
to adhere together in heaps or strings. The Torula multiplies 
in another way, by the process of endogenous division; no 
budding takes place, but the ‘‘ proto-plasm divides into (usually) 
four masses ; each of them surrounds itself with a cell-wall, and the 
whole are set free by the dissolution of the cell-wall of the parent.” 
(Huxley.) Reproduction further takes place by aeriel spores. 
The power of exciting fermentation is inherent in the 
Torula cells and not in the fluid part of yeast, for when 
they (and their minute germs) are separated from the fluid 
by a very fine filter, such as porous earthenware, the latter 
will not give rise to fermentation when added to a saccharine 
tea 
