Haeckel himself afterwards said that he only acceded to his father’s wish, that he should study medicine, with a botanical mental reservation. He thought of going through the discipline conscientiously until he became a physician, and then secure a place as ship’s doctor, and travel over the world and see the tropics. Things turned out very differently. He never became a medical man such as his father had wished, but he passed over the profession into zoology. Botany remained the lost and never-forgotten love of his youth. When we look back on his whole career we can see that he was, on the whole, fortunate. Zoology afforded a richer, more abundant, and more varied material at that time. It proved to be more “philosophical.” He went after his father’s asses and found a kingdom. But to him personally it seemed to be an unmistakable renunciation—the first in an active career that was to see many resignations.
“He goes farthest who does not know where he is going.”
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 in the same direction. The third member of the group, made professor in 1849, was Rudolf Virchow, a young teacher then in his best years. It was Virchow who did most to bring practical medicine into line with histology. As the vital processes in the human body seemed to him, with his strict histological outlook, to be traced back always to the tissue-building cells, he concluded that disease also, or the pathological condition of the body, and therefore the proper field of the medical man, was a process in these cells. Man seemed to him to be a “cell-state”: the tissues were the various active social strata in this state: and disease was, in its ultimate source, a conflict in the state between the citizens, the tissue-forming cells, that normally divide the work amongst them for the common good. Pathology must be cellular pathology. The science was already being taught by Virchow at Würtzburg, and the dry bones of it were covered with flesh for his hearers. But his ideas were not published until a few years afterwards (1858).
In the first three terms Haeckel studied chiefly under Kölliker and Leydig. They taught him animal and human embryology, as it was then conceived. Embryology was the science of the development of the individual animal or man, the description of the series of changes that the chick passes through in the egg or the human embryo in the womb. This science, also, had been profoundly affected by the invention of the microscope. Firstly, the spermatozoa, the active, microscopically small particles in the animal and human sperm, had been discovered. Then, in the twenties, Karl Ernst von Baer had discovered the human ovum. The relation of these things to the cell-theory was clear. It was indubitable that each of these male spermatozoa and each female ovum was a cell. They melted together and were blended into a new cell in the act of procreation, and from this, by a process of repeated cleavage of cells, the new individual was developed with all his millions of cells and all the elaborate tissues that these cells united to form. A whole world of marvellous features came to light, but the key to the unriddling of them was still wanting.
However, the Würtzburg school was at least agreed as to method, which was the main thing; its leaders were determined to press on to the solution of these problems on purely scientific lines. Everything was to be brought into a logical relation of cause and effect, and there was to be no intrusion of the supernatural, no mysticism. Natural laws must be traced in the life of the cells and in the history of the ovum and the embryo. The cells were to be regarded in the same way as the astronomer regards his myriads of glittering bodies. In this way the science of histology had been founded, and embryology had assumed a scientific character in the hands of Von Baer. The microscope kept the attention of students to facts, and did not suffer them to lose themselves in the clouds. Thus a foundation-stone was laid in Haeckel’s thoughts which he would never discard.
In the later years of the Darwinian controversy he was destined to come into sharp conflict with both Virchow and Kölliker. Each of them came to look on him as the sober hen does on the naughty chick it has brought into the world, that madly tries to swim on the treacherous waters of Darwinism. But forty years afterwards—after many a knife-edged word had been thrown in the struggle—the aged Kölliker was one of those who entered their names in the list of men of science who erected a bust in the Zoological Institute at Jena in honour of Haeckel’s sixtieth birthday.
However, it was a different, an apparently trivial, yet, as it turned out, most momentous interest that quickened him during these University years.
The impulse to microscopic research, that had led to the foundation of histology and embryology, had brought about a third great advance which had an important bearing on zoology. When we stroll along the beautiful shore of the Mediterranean at Naples to-day, with eyes bent on the blue surface from which Capri rises like a siren, and on the cloud-capped Vesuvius with its violet streaks of lava cutting across the green country, we notice in the foreground of the picture a stout building, with very large windows, planted with the boldness of a parvenu amongst the foliage. It is the “Zoological Station,” built by Dohrn, a German zoologist, at the beginning of the seventies. Anton Dohrn was one of Haeckel’s first pupils, and was personally initiated by him into the study of marine life, at Heligoland in 1865. Zoologists who work in the station to-day find it very comfortable. Little steamers with dipping apparatus bring the inhabitants of the bay to them. There is a large aquarium at hand. You sit down to your microscope, and work. The material is “fresh to hand” every day. There are now many of these stations at well-exposed spots on the coast in various countries—sea-observatories, as it were, in which the student examines his marine objects much as the astronomer observes his planets and comets and double stars at night. To-day, when a young man is taking up zoology, and he is asked what university he is going to, he may say that he is going down to the coast, to Naples, to do practical work. When the long vacation comes, swarms of professors go from the inland towns to one or other seaside place, as far as the purse will take them. All this is a new thing under the sun. The zoologist of the olden days sat in his study at home. He caught and studied whatever was found in his own district. The rest came by post—skins, skeletons, amphibians and fishes in spirit, dried insects, hard shells of crustacea, mussels and snails of all sorts; but only the shells always, the hard, dry parts of star-fishes, sea-urchins, corals, &c. Animals of the rarest character were thrown away because they could not very well be preserved in spirit and sent from the North Sea or the Mediterranean to Professor Dry-as-dust. In this state of things the advance in microscopic work brought no advantage. But at last it dawned on students that the sea is the cradle of the animal world. Whole stems of animals flourished there, and there only. Every wave was full of innumerable microscopic creatures, of the most instructive forms. Amongst them were found the young embryonic forms of familiar animals. At last the cry, “To the sea,” was raised. The older professor of zoology had suffered from a kind of hydrophobia. It was not possible to teach very much at Berlin about the anatomy, histology, and embryology of the sea-urchin from a few dried flinty shells. At Würtzburg, animals were subtly discussed by men who had never made a journey to see them, while they were trampled under foot every day by the visitors bathing in Heligoland. They must move. It was not necessary to go round the world: a holiday journey to the North Sea or the Mediterranean would suffice. Every cultured man had always considered that he must make at least one pilgrimage to classic lands before his education was complete. It was only a question of changing material. They were not to confine themselves to examining ruined temples and aqueducts, but to take their microscopes down to the coast, draw a bucketful of sea-water, and examine its living contents—the living medusa and sea-urchin, and the living world of the swarming infusoria. But it was like the rending of the great curtain of the temple. Zoology seemed to expand ten-fold, a hundred-fold, in a moment. A room in an obscure inn by the sea, a microscope, and a couple of glasses of salt-water with sediment every morning—and the finest studies at Paris and London were as ploughed land, without a single blade, in face of this revelation. It was a Noah’s ark in the space of a pinch of snuff.