Haeckel once applied this motto to himself and his star, in a humorous after-dinner speech. With this kind of safe predestination he reached Würtzburg in the autumn of 1852 as a medical student. Medicine had in those days received an entirely new theoretical basis from Würtzburg—a basis that was calculated to attract a young inquirer, who brought much more of the general Faust-spirit to his work than aspiration to the profession and the doctor’s cap, or the practical side. Let us recall for a moment how medicine had gradually reached the position of an independent science. Medicine was the outcome of a remote mythical epoch. It was content with the effect of certain venerable traditional medicaments on the living body, but knew little or nothing of the inner structure of the body on which it tried its drugs. The dissection and examination of even a corpse was regarded as a deadly sin, and was visited with secular punishment. Scientific medicine did not exist until this prohibition was removed; its first and most necessary foundation was anatomy, the science of the bodily structure and its organs. The art of “cutting up” bodies had seemed too revolting. Moreover, no sooner had the science of anatomy been founded than the range of the human eye itself was considerably enlarged. The microscope was invented. A new world came to light in the dissection of the body. Beyond their external appearance it revealed the internal composition of the various organs. The eye sees a shred of skin, a piece of intestine, or a section of the liver. The microscope fastens on a tiny particle of this portion of the body, and reveals in it a deeper layer of unsuspected structures. It is well known in the history of microscopic discovery that the more powerful lenses and the improved methods of research were only gradually introduced, and enabled students to found a new and much profounder anatomy. As soon as this science appeared it was given the special name of “histology,” or the science of the tissues (_hista_). Its particular achievement is the discovery that in man, the animal, and the plant, all the parts of the body prove, when sufficiently magnified, to be composed of small living elements, which are known as cells. The discovery of the cell was made in the latter part of the third decade of the nineteenth century. These cells join together in homogeneous groups in order to accomplish one or other function in the body, and thus form its “tissues.” Their intricate structure is unravelled by the histologist, microscope in hand. It is evident that in this way a new basis was provided for anatomy, and therefore also for medicine. In the fifties Würtzburg was the leading school of histology, or the science of these tissues composed of cells. Albert Kölliker, professor of anatomy there since 1847, published his splendid _Manual of Histology_ at the very time when Haeckel was studying under him. Franz Leydig, a tutor there since 1849, was working