750 K E N where he became a privat-docent, and abridged his name to Oken. As Lorenz Oken he published in 1802 his small work entitled Grundriss der Naturphilosophie, der Theorie der Sinne, und der darauf gegrilndeten Classification der Thiere, the first of the series of works which placed him at the head of the " natur-philosophie " or physio- philosophical school of Germany. In it he extended to physical science the philosophical principles which Kant had applied to mental and moral science. Oken had, however, in this application been preceded by Fichte, who, acknowledging that the materials for a universal science had been discovered by Kant, declared that nothing more was needed than a systematic co-ordination of these materials ; and this task Fichte undertook in his famous Doctrine of Science (Wissenschaftslehre), the aim of which was to construct a priori all knowledge. In this attempt, however, Fichte did little more than indicate the path ; it was reserved for Schelling fairly to enter upon it, and for Oken, following him, to explore its mazes yet farther, and to produce a systematic plan of the country so surveyed. In the Grundriss der Naturphilosophie of 1802 Oken sketched the outlines of the scheme he afterwards devoted himself to perfect. The position he advanced in that re markable work, and to which he ever after professed ad herence, is this, " that the animal classes are virtually nothing else than a representation of the sense-organs, and that they must be arranged in accordance with them." Agreeably with this idea, Oken contends that there are only five animal classes : (1) the Dermatozoa, or Inverte brates; (2) the Glossozoa, or Fishes, as being those animals in which a*lrue tongue makes, for the first time, its appear ance ; (3) the Rhinozoa, or Reptiles, wherein the nose opens for the first time into the mouth and inhales air ; (4) the Otozoa, or Birds, in which the ear for the first time opens externally ; and (5) the Ophthalmozoa, or Mammals, in which all the organs of sense are present and complete, the eyes being movable and covered with two lids. In 1805 Oken made another characteristic advance in the application of the a priori principle, by a book on generation (Die Zeugung, Frankfort), wherein he main tained the proposition that " all organic beings originate from and consist of vesicles or cells. These vesicles, when singly detached and regarded in their original process of production, are the infusorial mass or protoplasma (ur- schleini) whence all larger organisms fashion themselves or are evolved. Their production is therefore nothing else than a regular agglomeration of Infusoria, not, of course, of species already elaborated or perfect, but of mucous vesicles or points in general, which first form themselves by their union or combination into particular species." This doctrine is strikingly analogous to the generalized results of the ablest microscopical observations on the de velopment of animal and vegetable tissues which have been prosecuted of late years. One year after the production of this remarkable treatise, Oken advanced another step in the development of his system, and in a volume published in 1806, in which Kieser assisted him, entitled Beitrdge zur vergleichenden Zoologie, Anatomic, und Physiologic, he demonstrated that the intestines originate from the umbilical vesicle, and that this corresponds to the vitellus or yolk-bag. Caspar Fried- rich Wolff had previously proved this fact in the chick (Theoria Generationis, 1774), but he did not see its applica tion as evidence of a general law. Oken showed the im portance of the discovery as an illustration of his system. In the same work Oken described and recalled attention to the corpora Wolffiana, or "primordial kidneys," as they are now termed and recognized. The reputation of the young privat-docent of Gottingen had meanwhile reached the ear of Goethe, and in 1807 Oken was invited to fill the office of professor extraordi- narius of the medical sciences in the university of Jena. He accepted the call, and selected for the subject of his inaugural discourse his ideas on the " Signification of the Bones of the Skull," based upon a discovery he had made in the previous year. This famous lecture was delivered in the presence of Goethe, as privy-councillor and rector of the university, and was published in the same year, with the title, Ueber die Bedeutung der Schadelknochen. With regard to the origin of the idea, Oken narrates in his Isis that, walking one autumn day in 1806 in the Harz forest, he stumbled upon the blanched skull of a deer, picked up the partially dislocated bones, and con templated them for a while, when the truth flashed across his mind, and he exclaimed, "It is a vertebral column ! " At a meeting of the German naturalists held at Jena some years afterwards Professor Kieser gave an account of Oken s discovery in the presence of the grand-duke, which account is printed in the Tageblatt, or "proceedings," of that meeting. The professor states that Oken communi cated to him his discovery when journeying in 1806 to the island of Wangeroog. On their return to Gottingen Oken explained his ideas by reference to the skull of a turtle in Kieser s collection, which he disarticulated for that purpose with his own hands. "It is with the greatest pleasure," writes Kieser, " that I am able to show here the same skull, after having it thirty years in my collection. The single bones of the skull are marked by Oken s own handwriting, which may be so easily known." There was a cause, as we shall presently see, for this circumstantial testimony. Oken, having delivered and printed his introductory lec ture in 1807, informs us (Isis, No. 7) that he presented copies to Goethe and to other members of the grand-duke s Government. " Goethe was so pleased with my discovery as to invite me to stay with him during the Easter week of 1808 in his house at Weimar, which invitation I accepted." The range of Oken s lectures at Jena was a wide one, and they were highly esteemed. They embraced the sub jects of natural philosophy, general natural history, zoology, comparative anatomy, the physiology of man, of animals, and of plants. The spirit with which he grappled with the vast scope of science is characteristically illustrated in his essay Ueber das Universum als Fortsetzung des Sinnensys- tems, 1808. In this work he lays it down that " organism is none other than a combination of all the universe s activities within a single individual body." This doctrine led him to the conviction that " world and organism are one in kind, and do not stand merely in harmony with each other." In the same year he published his Erste Ideen zur Theorie des Lichts, &c., in which he advanced the propo sition that " light could be nothing but a polar tension of the ether, evoked by a central body in antagonism with the planets, and heat was none other than a motion of this ether," a sort of vague anticipation of the doctrine of the "correlation of physical forces." In 1809 Oken extended his system to the mineral world, arranging the ores, not according to the metals, but agree ably to their combinations with oxygen, acids, and sulphur. In 1810 he summed up his views on organic and inorganic natures into one compendious system. The first edition of the Lehrbufh der Naturphilosophie appeared in that and the following years, in which he sought to bring his different doctrines into mutual connexion, and to "show that the mineral, vegetable, and animal kingdoms are not to be arranged arbitrarily in accordance with single and isolated characters, but to be based upon tte cardinal organs or anatomical systems, from which a firmly established number of classes would necessarily be evolved ; that each class, A
