One result of the introduction of types into chemical science, associated as it was with the unitary view of compound radicles, was to overthrow that definition of organic chemistry which had for some time prevailed, and which stated that organic chemistry is "the chemistry of compound radicles." Compound radicles, it is true, were more used in explaining the composition and properties of substances obtained from animals and vegetables than of mineral substances, but a definition of one branch of a science which practically included the other branch, from which the first was to be defined, could not be retained. Chemists became gradually convinced that a definition of organic chemistry was not required; that there was no distinction between so-called organic and inorganic compounds; and they have consented, but I scarcely think will much longer consent, to retain the terms "organic" and "inorganic," only because these terms have been so long in use. The known compounds of the element carbon are so numerous, and they have been so much studied and so well classified, that it has become more convenient for the student of chemistry to consider them as a group, to a great extent apart from the compounds of the other elements; to this group he still often gives the name of "organic compounds." * * * * * Liebig continued to hold the chair of Chemistry in the University of Giessen until the year 1852, when he was induced by the King of Bavaria to accept the professorship of the same science in the University of Munich. During the second quarter of this century Giessen was much resorted to by students of chemistry from all parts of the world, more especially from England. Many men who afterwards made their mark in chemical discovery worked under the guidance of the professor of Stockholm, but Giessen has the honour of being the place where a well-appointed chemical laboratory for scientific research was first started as a distinctly educational institution. The fame of Liebig as a discoverer and as a teacher soon filled the new institution with students, who were stirred to enthusiasm as they listened to his lectures, or saw him at work in his laboratory. "Liebig was not exactly what is called a fluent speaker," says Professor Hofmann, of Berlin, "but there was an earnestness, an enthusiasm in all he said, which irresistibly carried away the hearer. Nor was it so much the actual knowledge he imparted which produced this effect, as the wonderful manner in which he called forth the reflective powers of even the least gifted of his pupils. And what a boon was it, after having been stifled by an oppressive load of facts, to drink the pure breath of science such as it flowed from Liebig's lips! what a delight, after having perhaps received from others a sack full of dry leaves, suddenly in Liebig's lectures to see the living, growing tree!... We felt then, we feel still, and never while