596 FERMENTATION AS A CAUSE OF VARIOUS DISEASES. 
almost entirely free from arsenic. This method may become 
of some practical importance. One of the principal makers 
of emetic tartar informs me that the black antimony lately in 
the market has been much more contaminated by arsenic 
than was formerly the case, and that it causes much trouble 
with the mother-liquors. 
Impurity may exist to a much greater extent than that now 
recorded. Thus, Gmelin quotes Serullas to show that all 
German and French black antimony, excepting that of 
Montlu 9 on, contains from I '6 to 5 per cent, of arsenic. 
It is evident that those who may unwittingly vend the 
contaminated samples incur the risk of being held respon¬ 
sible for results. 
So long as sulphide of arsenic is present, and its noxious 
or innocuous quality depends upon the nature of the fluids 
which it meets with in the stomach, there will be a very 
disagreeable uncertainty about the use of the crude drug. 
ON FERMENTATION AS A CAUSE OF VARIOUS DISEASES. 
By M. Polli. 
Chemists who have for several years been successfully 
studying the phenomena of fermentation have observed that 
this mode of reaction, among organic principles, possesses an 
importance much greater than is generally supposed. It is, 
in fact, to fermentation that the spontaneous decomposition 
of animal and vegetable tissues is owing, as dry-rot, ere- 
macausis, gangrene, &c., and the whole series of successive 
transformations which organic matters undergo until they 
are converted into water, carbonic acid, ammonia, and mineral 
matters. It is by fermentation that fatty bodies give glyce¬ 
rine ; that salicine furnishes glucose; that myronate of 
potash is converted into essential oil of mustard; that neu¬ 
tral substances, such as urea and allantoin, form ammonia; 
that amygdaline produces the poisonous substances, oil of 
bitter almonds and Prussic acid. 
Ferments act by contact or by catalysis. Sometimes they 
are living creatures; sometimes very active unorganized sub¬ 
stances. Diastase, emulsine, and pepsine act as ferments. 
They can cause organic substances to double, become hy¬ 
drated, or isomeric. 
According to M. Polli, there exists considerable analogy 
between the processes of fermentation and several organic 
