Part 7

He had conceived the 'unity of organic composition,' meaning that there is only one plan of construction,--the same principle, but varied in its accessory parts. In 1830, when Geoffroy proceeded to apply to the Invertebrata his views as to the uniformity of animal composition, he found a vigorous opponent in Cuvier. Geoffroy, like Goethe, held that there is in Nature a law of compensation, or balancing of growth, so that if one organ take on an excess of development, it is at the expense of another part; and he maintained that, since Nature takes no sudden leaps, even organs which are superfluous in any given species, if they have played an important part in other species of the same family, are retained as rudiments, which testify to the permanence of the general plan of creation. It was his conviction that, owing to the conditions of life, the same forms had not been perpetuated since the origin of all things, although it was not his belief that existing species were becoming modified. Cuvier, on the other hand, maintained the absolute invariability of species, which, he declared, had been created with regard to the circumstances in which they were placed, each organ contrived with a view to the function it had to fulfil,--thus putting the effect for the cause ('Encyclopædia Britannica,' 9th edition, vol. xxi., p. 171).

GEORGE CUVIER was born in 1769 at Montbéliard, in the department of Doubs, which at that time belonged to Württemberg. He was educated at Stuttgart, and studied political economy. While acting as private tutor to a French family in France he followed his favourite pursuit, the study of natural sciences. Geoffroy Saint-Hilaire heard of him, and appointed him assistant in the department of comparative anatomy in the Musée d'Histoire Naturelle. In 1799 he was elected Professor of Natural History at the Collège de France, and soon after he became Perpetual Secretary of the Institut National. In 1831, a year before his death, Louis Philippe raised him to the rank of a peer of France.

Cuvier was the first to indicate the true principle upon which the natural classification of animals should be based--namely, their structure. It is the study of the anatomy of the creatures and their comparison which affords the only sound basis of a classification. The work which had the greatest influence upon the scientific public is his 'Règne animal distribué d'après son Organisation,' 1817. The system which he propounded in this book gradually came to have almost world-wide fame, and, in spite of its many obvious deficiencies, still lingers in some of our most recent text-books.

A standard work is his 'Leçons d'Anatomie comparée,' and, in truth, he is the founder of that kind of comparative anatomy which was brought to such a high state by his pupil, the late Sir Richard Owen. Cuvier discovered the law of 'correlation of growth,' and was the first to apply this law to the reconstruction of animals from fragments: see his monumental work entitled 'Recherches sur les Ossemens fossiles,' 1812.

Cuvier, however, as a strict matter-of-fact man, was incapable of appreciating the speculative conclusions which were drawn by his contemporaries Saint-Hilaire and Lamarck. On the contrary, he firmly stuck to the doctrine of the immutability of species; and, in order to account for the existence of animals whose kind exists no longer, he invented the famous doctrine of successive cataclysms.

KARL ERNST VON BAER was born in 1792 in Esthonia, studied at Dorpat and then at Würzburg, where Döllinger introduced him to comparative anatomy. For a few years he was a Privat-docent at Berlin; then he went to Königsberg as Professor of Zoology and Embryology. In 1834 he became an Academician at St. Petersburg, where for many years he was occupied with the most varied studies, chiefly geographical and ethnological. The last years of his long, active life he spent in contemplative retirement on his paternal estate, and he died at Dorpat in 1876.

While still at Würzburg he induced his friend Pander, a young man of means, to study the development of the chick; and Pander was the first to start the theory of the germinal layers from which all the organs arise. Baer, however, continued these researches in Königsberg, and after nine years' labour produced his epoch-making work, 'Ueber Entwicklungsgeschichte der Thiere: Beobachtung und Reflexion,' Königsberg, 1828. Nine years later he completed the second volume. He established upon a firm basis the theory of the germinal layers, and by further 'reflexions' arrived at the elucidation of some of the most fundamental laws of biology. For example, in the first volume he made the following prophetic statement: 'Perhaps all animals are alike, and nothing but hollow globes at their earliest developmental beginning. The farther back we trace their development, the more resemblance we find in the most different creatures. And this leads to the question whether at the beginning of their development all animals are essentially alike, and referable to one common ancestral form. Considering that the "germ" (which at a certain stage appears in the shape of a hollow globe or bag) is the undeveloped animal itself, we are not without reason for assuming that the common fundamental form is that of a simple vesicle, from which every animal is evolved, not only theoretically, but historically.'

This statement is all the more wonderful when we consider that the cells, the all-composing individual units, were not discovered until ten years later.

In 1829 Baer discovered the human egg, and later the chorda dorsalis. In an address delivered in 1834, entitled 'The Most Universal Law of Nature in all Development,' he explained that only from a most superficial point of view can the various species be looked upon as permanent and immutable types; that, on the contrary, they can be nothing but passing stages, or series of stages, of development, which have been evolved by transformation out of common ancestral forms.

JOHANNES MUELLER, born at Coblenz in 1801, established himself as Privat-docent at Bonn, where in 1830 he became Professor of Physiology. In 1833 he accepted the Chair of Anatomy and Physiology at Berlin, where he died in 1858.

He was one of the most distinguished physiologists and comparative anatomists. By summarizing the labours and discoveries already made in the field of physiology, by reducing them to order, and abstracting the general principles, he became the founder of modern physiology. But he was scarcely less distinguished by his researches in comparative anatomy. His 'Vergleichende Anatomie der Myxinoiden,' in Abhandlungen der Berliner Akademie, 1835-45, and 'Ueber die Grenzen der Ganoiden' (ibid., 1846), are standard works of lasting value.

Mueller exercised a stimulative influence as a teacher. Many well-known men--such as Helmholtz, Gegenbaur, Bruecke the physiologist, Guenther the zoologist, Virchow the pathologist, Koelliker and Haeckel--have been his pupils.

RUDOLPH VIRCHOW was born in 1821 at Schievelbein, a small town in Eastern Pomerania. He studied medicine in Berlin as a pupil of Johannes Mueller, and went in 1849 to Würzburg, where, under the influence of Koelliker, and Leydig the pathologist, he laid the foundation of an entirely new branch of medical science--that of 'cellular pathology.' Since 1856 he has filled the principal Chair of Pathology at Berlin. In 1892 he received the Copley medal of the Royal Society.

'His contributions to the study of morbid anatomy have thrown light upon the diseases of every part of the body; but the broad and philosophical view he has taken of the processes of pathology has done more than his most brilliant observations to make the science of disease.

'In pathology, strictly so called, his two great achievements--the detection of the cellular activity which lies at the bottom of all morbid as well as normal physiological processes, and the classification of the important group of new growths on a natural histological basis--have each of them not only made an epoch in medicine, but have also been the occasion of fresh extension of science by other labourers' (Proc. Royal Soc., 1892).

Virchow has not confined himself to medicine. He takes the keenest interest in anthropology and ethnology, on which subjects he has contributed many papers. Together with his colleagues Helmholtz the physicist, and Du Bois Reymond the physiologist, he has taken a leading place in the spreading of natural science; but, unfortunately, he did not take to the doctrine of Evolution, and for the last thirty years has been its declared antagonist, rarely missing an opportunity of denouncing everything but descriptive anatomy and zoology as the unsound speculations of dreamers. This has on more than one occasion brought him into sharp conflict with Haeckel. His activity is astonishing, especially if it be remembered that Virchow has for many years been one of the most conspicuous leaders of the Progressists and Radicals in the German Parliament and Berlin town-council.

EDWARD DRINKER COPE was born at Philadelphia, Pa. After studying at several Continental Universities, especially at Heidelberg, he became first Professor of Natural Science at Haverford College, and later Professor of Geology and Mineralogy. He died at an early age in 1897. As a member of various geological expeditions and other surveys, he explored chiefly Kansas, Wyoming, and Colorado; and he published many most suggestive papers on the fossil vertebrate fauna of North America, and on classification especially of Amphibia and Reptiles.

Among works of a more general philosophical scope may be mentioned 'The Origin of the Fittest,' 1887, and his latest work, 'The Primary Factors of Organic Evolution,' 1896.

ALBERT VON KOELLIKER, born in 1817, became Professor of Anatomy at Würzburg. His earlier studies and discoveries contributed considerably to the systematic development of the cell theory. In 1844 he observed the division and further multiplication of the original egg cell. Next year he showed the continuity between nerve cells and nerve fibres in the Vertebrata; later, that the non-striped or smooth muscular tissue is composed of cellular elements. He demonstrated that the Gregarinæ are unicellular creatures. In 1852 he went with his younger friend Gegenbaur to Messina, where he studied especially the development of the Cephalopoda (cuttlefishes and allies); and he produced a magnificent work on Alcyonaria, Medusæ, and other allied forms. He elucidated the development of the vertebral column, especially with reference to the notochord.

In 1848 he founded, together with Th. von Siebold, the famous Zeitschrift für wissenschaftliche Zoologie.

A standard work on mammalian embryology is his 'Entwicklungsgeschichte des Menschen und der höheren Thiere,' a text-book of which the second edition appeared in 1879.

At the anniversary meeting of 1897 he received the Copley medal, the highest honour which the Royal Society can bestow.

CARL GEGENBAUR was born on August 21, 1826, in Bavaria. He studied medicine and kindred subjects in Würzburg, and as a pupil of Johannes Mueller in Berlin.

In 1852 he went with Koelliker to Messina to study the structure and development of the marine fauna. Important papers on Siphonophora, Echinoderms, Pteropoda, and, later, Hydrozoa and Mollusca, were the result. Soon after his return he was offered the chair of Anatomy at Jena, and at this retired spot he produced his most important works, devoting himself more and more to the study of the Vertebrata. Since 1875 he has held the Chair of Anatomy at Heidelberg.

In 1859 he published his 'Principles of Comparative Anatomy'; but in 1870 he remodelled it completely, the theory of descent being the guiding principle. These 'Grundzüge' were followed by a somewhat more condensed 'Grundriss,' the second edition of which was published in 1878, and has been translated into French and English. In the meantime he had broken new ground by the development and treatment of certain problems concerning the composition and origin of the limbs, the shoulder-girdle and the skull, researches which are embodied in his 'Untersuchungen zur vergleichenden Anatomie der Wirbelthiere,' 1864-65-72.

In 1883 he brought out a text-book on human anatomy. This also marked a new epoch, because for the first time, not only the nomenclature, but also the general treatment of human anatomy, was put upon a firm comparative anatomical basis. The success of this work is indicated by the fact that it reached the sixth edition in 1897.

Lastly, in 1898, appeared the first volume of what may be called his crowning work, 'Vergleichende Anatomie der Wirbelthiere.'

Gegenbaur is universally recognised, not only as the greatest living comparative anatomist, but also as the founder of the modern side of this science, by having based it on the theory of descent.