beautifully shown than in the field of neurology, which numbers among its great men Deiters, His, Gerlach, and Nissl from Germany; Purkinje, a Bohemian; Golgi, an Italian; Forel, a Swiss; Nansen, a Norwegian; and Barker, Donaldson, and Hodge, Americans To this list must be added the euphonious name of Ramon y Cajal, a Spaniard, who ranks most renowned among the army of laborers who have enlightened us in regard to that most important factor in the life of the growing child, his nervous system.

CHAPTER III

THE SCIENTIFIC STUDY OF THE CHILD

After all has been said, the most profoundly revolutionary and productive event in the history of biological thought was the publication, in 1859, of Darwin's "Origin of Species." Everything in nature has a pedigree, a history. An organism is really not understood even when anatomy, physiology, and histology combine to explain its structure and mechanism in minute detail. There always remains the great historical question of origin and development. This was Darwin's problem, and to its solution he consecrated his genius. As early as 1835, on his voyage around the world as naturalist on his Majesty's ship the Beagle, the problem occurred to him. In his famous letter to the botanist Hooker he says: "I was so struck with the distribution of the Galapagos organisms and with the character of the American fossil mammifers that I determined to collect blindly every sort of fact which would bear in any way on what are species. I have read heaps of agricultural and horticultural books and have never ceased collecting facts."

The origin and development of species is a venerable problem. Aristotle spoke of a principle of perfection running through the universe. The medieval scholars naturally accepted the Hebrew account of the genesis of all things and the preservation of species in Noah's ark. In fact, the belief in the immutability and special creation of species persisted into the nineteenth century. Linnæus, the great

naturalist whose system of nomenclature did so much to bring order and classification into the accumulating knowledge about plants and animals, believed all species were created in the beginning. He was acquainted with only four thousand species of animals, whereas it is now known that the species, extinct and living, must easily number a million. As the fossil remains of extinct creatures came to be better known, the idea of the fixity of species became more and more untenable. Buffon, Erasmus Darwin, and Goethe all doubted such fixity. Cuvier, to defend the prevailing concept, presented the theory of cataclysms, which asserted that there were successive eras of destruction and creation, and fossils were the remnants of these ancient cataclysms. Lamarck held that these fossils represented the ancestors of living forms. He worked out a comprehensive theory of descent and mutability of species which entitles him to be called the father of evolutionary thought; but he was neither happy nor fruitful in suggesting the way in which species originate and are transformed. Charles Darwin, after twenty-five years of quiet, patient study, presented an explanation of the way in his epoch-making book.

His explanation was the principle of natural selection, which Romanes calls the most important idea ever conceived by man. This principle, like a telescope, freed man from the narrow horizon of the present and the recent, and allowed him to glimpse down the deep perspective of the geologic past. It gave him some conception of how all the manifold earthly flora and fauna came to be what they are. Not only in the special fields of zoölogy and botany did it extend the vision, but in every department of thought the interpretations of men were given a new range and depth.

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Thus sociology, anthropology, politics, and even theology reshaped their subject matter along the new genetic lines. Embryology became less purely anatomical- became almost romantically historical" under the new Darwinian influence. Through the labor of Fritz Müller, Balfour, Marshall, and Haeckel, one of the most wonderful of all scientific generalizations was worked out, the theory of recapitulation, which holds that animals, in their individual unfoldment, to a considerable degree recapitulate the phases of their phyletic or racial development.

So extensively was the intelligence of the age affected that the nineteenth century has even been called Darwin's century. "Whatever the verdict of posterity," - quoting from Huxley, the ardent champion of Darwinism, -—" the broad fact remains that since the publication, and by reason of the publication, of the Origin of Species,' the fundamental concepts and aims of the students of living nature have been completely changed."

The child is a part of living nature. The greatest modern student of the child is G. Stanley Hall. When the history of science is seriously recorded, his name will be linked with that of Charles Darwin. Both are large-visioned interpreters of nature, combining scientific methods with a philosophic temper. Darwin applied his genius to the great genetic problems of biology; Hall is the Darwin of psychology. Both have gleaned the fields of paleontology, geology, anthropology, botany, and zoölogy, to set forth illuminating interpretations concerning the development and expression of life. In many fields their studies overlap. Indeed, the psychology of Hall is biological; he has brought these two sciences into intimate and fruitful union. Darwin could limit himself, rather strictly, to measurable, verifiable data, in his studies of the plant and animal kingdom; Hall's