ADVANCED BY LIEBIG AND OTHERS. 
9 
(glucose) is of necessity precursory to the vinous fermenta- 
tion, wherever the saccharine matter is not naturally in that 
state. But when grape sugar is fermented, the disparity 
between the weight of the sugar and its products no longer 
exists; the weight of the resulting alcohol and carbonic 
acid, are just equal to that of the sugar out of which they 
are generated. 
Independently of any agency of this kind, which seems 
even more probable in the case of some species of infection 
than in that of fermentation, I conceive that the present 
state of our knowledge does not allow of our comprehend- 
ing the means by which bodies, whether organic or inor- 
ganic, are endowed with the powers ascribed to catalysis ; 
but that we have great reason to believe that these powers, 
as well as all the properties which ultimate elements acquire 
by diversity of association, as in compound radicals, are due 
to the same source as the phenomena of galvanic electricity. 
It is well known, that although pure zinc is not suscep- 
tible of oxidation by exposure to dilute sulphuric acid, yet 
that, when containing minute proportions of other metals, 
as in the case of commercial zinc, it becomes liable to rapid 
oxidation by the same reagent. This Faraday has explain- 
ed by the electro-chemical influence of the comparatively 
electro-negative metallic particles distributed throughout 
the mass of the zinc, which he conceived to be productive 
of as many local galvanic circuits with corresponding elec- 
trolytic currents. This explanation has, I believe, been 
universally sanctioned, and was consistent with the previ- 
ous discovery of Sturgeon, that when, by amalgamating 
the surface with mercury, a metallic communication was 
made between the electro-positive and electro-negative 
particles, so as to prevent the formation of electrolytic cur- 
rents through the oxidizing liquid, the zinc became nearly 
as insusceptible of union with oxygen, as when in a pure 
state. 
Nevertheless, either when pure, or when amalgamated, 
