The progress of medicine, like that of other sciences, depends on the leaders, of whom there are two classes. To the one class belong those to whom the slow, steady and safe advances are due. These leaders are identified with established lines of research or practice and stand in the front rank of their profession, from the best elements of which they are not separated by a conspicuous gap. Their number is not small, and they usually hold the first positions in the gift of the profession, while they are, as a rule, the distinguished pupils of masters of their own type.
To the other class, however, belong those who precipitate, as it were, long-suspended and hitherto unperceived elements of knowledge, so that orderly truth seems to crystallize in the twinkling of an eye out of what appeared hitherto but a baffling jumble of facts. Men of this class are