It is one of the curious features of history that genuine worth of human accomplishment is almost in inverse ratio to the popularity it obtains in the generation in which it is produced. Supremely great work is rarely appreciated at anything like its proper value, by contemporaries. This principle is true apparently in all fields of human endeavor. In literature and in art it is a commonplace. But also, surprising though it may be, in science and in social betterment the rule holds a prominent place. It is nearly always the sign of only passing merit when any work secures the plaudits of its own generation. Brilliant theories are often immediately hailed with universal acclaim, while ground-breaking observations that are really great discoveries are apt to be neglected. The really new discovery is so novel that men cannot appreciate it at once. It is so different from their ordinary modes of thinking that they cannot place it properly. Its complete significance fails them. This has been true for our nineteenth century biology almost more strikingly than for any other department of knowledge. Our many avenues of publicity instead of heralding abroad the great observations as soon as they have been made, in order to enable others to continue the work that the master mind has begun, have been only too constantly crowded with new opinions, novel theories, taking hypotheses, all attracting attention that they did not deserve. Men like Theodore Schwann, the father of the cell doctrine, are not apt to be so well known as the suggestor of some {254} striking bit of theory. Even the great biologists, such as Darwin himself, are known rather for their insubstantial theories than for their substantial additions to biological knowledge by patient observation and genial penetration into the secrets of nature. It is perhaps a warning to the modern physician who realizes this state of affairs, not to take the popular theories even in his own branch of biology as the current coin of truth. Theories pass, but observations endure. Auenbrugger's new method of tapping the chest in order to elicit its varying sounds looked even more childish than Galvani's acceptance of the position of dancing master to a frog, but their observations thus made continued the germs of undying truth. While the name and the life of Theodore Schwann are but little known by the general public, his work is very thoroughly appreciated by those who have made special studies in biology, and few men in the progress of that science are considered to hold as high a place as that assigned to him. A study of the life of Schwann will serve to show not only that he eminently deserves this honor which has come to him, but will also bring into evidence the fact that his career deserves to be better known popularly, because it illustrates very well the typical mode of life in which great scientists are nurtured and the methods of investigation by which great discoveries are made.