Foremost among the workers who rendered this epoch of organic
chemistry memorable were Justus Liebig in Germany and Jean
Baptiste Andre Dumas in France, and their respective pupils,
Charles Frederic Gerhardt and Augustus Laurent. Wohler, too,
must be named in the same breath, as also must Louis Pasteur,
who, though somewhat younger than the others, came upon the scene
in time to take chief part in the most important of the
controversies that grew out of their labors.

Several years earlier than this the way had been paved for the
study of organic substances by Gay-Lussac's discovery, made in
1815, that a certain compound of carbon and nitrogen, which he
named cyanogen, has a peculiar degree of stability which enables
it to retain its identity and enter into chemical relations after
the manner of a simple body. A year later Ampere discovered that
nitrogen and hydrogen, when combined in certain proportions to
form what he called ammonium, have the same property. Berzelius
had seized upon this discovery of the compound radical, as it was
called, because it seemed to lend aid to his dualistic theory. He
conceived the idea that all organic compounds are binary unions
of various compound radicals with an atom of oxygen, announcing
this theory in 1818. Ten years later, Liebig and Wohler undertook
a joint investigation which resulted in proving that compound
radicals are indeed very abundant among organic substances. Thus
the theory of Berzelius seemed to be substantiated, and organic
chemistry came to be defined as the chemistry of compound
radicals.

But even in the day of its seeming triumph the dualistic theory
was destined to receive a rude shock. This came about through