Experience (Education) Has Produced Development.-In man we find that the cerebrum is vastly larger proportionally than in any other animal, and also that the frontal areas are for the first time prominent. Even in human beings we find that there is a great difference between the development of the frontal lobes of the lower and the higher races, and between children and adults. This is very significant educationally. It represents again, both cause and effect; possibilities and resultants of education. There is absolutely no question that the adult with the welldeveloped frontal brain areas is capable of thinking, reasoning, and willing in a way impossible to a child in which this development has not yet taken place. Similar differences between civilized and primitive man are equally apparent. It is also thoroughly demonstrable that education will tend to produce this development, or lack of it cause degeneration and atrophy. Venn studied the growth of the heads of Cambridge students and found that the heads of the best students grew longest and largest. Measurements secured before and after their university course showed that their cranial growth was greater than in non-students at corresponding periods. Investigations show that loss of brain weight, common to middle life and old age, does not take place so early nor so rapidly in the case of eminent men as in others. Although their brains have an inherited initial superiority, yet neurologists believe that there is no doubt that judicious mental exercise postpones decline. Donaldson, on the authority of Bischoff, says that the final decrease in the weight of the encephalon usually begins in men at about fifty-five years, and in women some years earlier. His curves indicate that the decline in the weight of the brains of eminent men is deferred till after sixty-five years. This, however, should not seem strange. Persons who maintain a vigorous muscular tone through rational physical exercise preserve their muscular vigor until a later age than those who have never cultivated their muscles. 1 Growth of the Brain, p. 325. 1 2 Galton regards proper exercise of the brain as a prerequisite of growth and a lack of it as a cause of degeneration. He wrote: "Although it is pretty well ascertained that in the masses of the population the brain ceases to grow after the age of nineteen, or even earlier, it is by no means so with university students." Venn wrote: "Comparing the 'head volumes' of the students, two facts claim notice, viz., first, that the heads of the high honor men are distinctly larger than those of the pass men; and second, that the heads of all alike continue to grow for some years after the age of nineteen." Consequently the measurements so carefully made by Venn are exceedingly significant. 3 Has Evolution Ceased? It is very interesting to consider whether specialization has reached the limit in the case of man's brain and psychic life. John Fiske wrote, as a chapter heading, these striking words: "On the earth there will never be a higher creature than man." Drummond in his chapter on the arrest of the body,' commenting upon the statement, says: "It is a daring prophecy, but every probability of science attests the likelihood of its fulfilment. The goal looked forward to from the beginning of time has been attained. Nature has succeeded in making a man; she can go no further; organic evolution has done its work." While acknowledging that psychical evolution is the type of all further human progress, yet we should not regard present physical development as by any means complete, nor the present type of man as perfect. "Man is the tadpole of what he is to be," the favorite phrase of Dr. G. Stanley Hall, is much nearer the truth. Struggle for still higher ideals than have ever been held will tend to develop a higher type of psychic life than any yet realized; and as mental life in all its phases of development has been paralleled by nervous and muscular development and has rendered the psychical evolution possible, may we not expect still higher development of both physical and mental life? Because of psycho-physical parallelism it must follow that if further 1 Nature, 41: 454. Destiny of Man, p. 26. "Nature, 41: 452. progress in mental life is to be attained in any direction, there must be corresponding structural adaptation of the physical organism. For example, in order to attain a higher appreciation of music, it is undoubtedly true that a more delicate auditory organism must be evolved. And with a constantly heightening ideal of music and a struggle to cultivate better understanding and appreciation this conscious selection must have as one effectthat of a more highly developed organism. Similarly more sensitive visual organs may be developed which would be sensitive to tints and colors and fine shades of difference not now possible to the imperfect eye. The sense organs of touch may become so delicate that grades of workmanship and professional skill in the artist, the physician, etc., hitherto undreamed of, may be made possible. Of course, some organs and powers may degenerate, but indefinite variation and change are not only possible but extremely probable. Within historic times, even in a few generations, I am pleased to believe, permanent modifications have taken place in man's brain and sense organs through cultivation of powers present and in response to the struggle for the attainment of higher ideals. We do not marvel when the breeder produces complete transformation through selection and the emphasis of desirable qualities. New breeds of horses and dogs, unrecognizable as related to the old through outward appearance, and vastly superior in mental qualities, are secured in a few generations. "Shall it stop here? Shall it not be carried forward on a higher plane by the conscious effort of man? Is not all civilization, all culture, all education a voluntary process of cephalization? Here, also, there must prevail the same law of progressive domination of the higher over the lower, of the distinctively human over the animal, of mind over body; and in the mind, of the higher faculties over the lower, the reflective over the perceptive, and of the moral character over all. In all your culture be sure that you strive to follow this law of evolution." 1 Le Conte, Comparative Physiology and Morphology of Animals, p. 83. CHAPTER IV THE THEORY OF RECAPITULATION 1 Progressive Development of the Individual. All individuals begin life as a single cell and it is only after gradual differentiation and specialization that complex animal forms are evolved. Wallace remarks apropos of this: "The progressive development of any vertebrate from the ovum or minute embryonic egg affords one of the most marvellous chapters in natural history. We see the contents of the ovum undergoing numerous definite changes; its interior dividing and subdividing till it consists of a mass of cells; then a groove appears marking out the median line or vertebral column of the future animal, and thereafter are slowly developed the various essential organs of the body." Huxley remarks in the same connection after describing the progressive changes in the canine embryo: "The history of the development of any other vertebrate animal, lizard, snake, frog, or fish, tells the same story. There is always to begin with an egg having the same essential structure as that of the dog: the yolk of the egg undergoes division or segmentation, as it is called, the ultimate products of that segmentation constitute the building materials for the body of the young animal, and this is built up round a primitive groove, in the floor of which a notochord is developed. Furthermore, there is a period in which the young of all these animals resemble one another, not merely in outward form, but in all essentials of structure, so closely that the differences between them are inconsiderable, while in their subsequent course they diverge more and more widely from one another. And it is a general law that the more closely any animals resemble one another in adult 1 Darwinism, p. 448. structure, the longer and more intimately do their embryos resemble one another: so that, for example, the embryos of a snake and of a lizard remain like one another longer than do those of a snake and of a bird; and the embryos of a dog and of a cat remain like one another for a far longer period than do those of a dog and a bird; or of a dog and an opossum; or even those of a dog and a monkey." 1 Resemblances of Embryos to Lower Adult Forms.-It has long been observed that the embryos of the higher animals at different stages resemble somewhat the adult forms of various lower species. The more immature the embryo the lower the species resembled, and the more mature the embryo the higher the species which it approximates. In the case of animals which undergo metamorphoses in attaining adult life the immature stages so completely resemble other adult forms that they are frequently regarded as another species. For example, moths and butterflies in the larval stage would naturally be classed with the worms by the unscientific. The young of frogs and toads, the tadpoles, are animals fitted to live in water only, and certainly would be classed with fishes if it were not known what subsequent metamorphoses would take place. Marshall wrote: "Everyone knows that animals in the earlier stages of their existence differ greatly in form, in structure, and in habits from the adult condition. A lung-breathing frog, for example, commences its life as a gill-breathing tadpole; and a butterfly passes its infancy and youth as a caterpillar. It is clear that these developmental stages, and the order of their occurrence, can be no mere accidents; for all the individuals of any particular species of frog, or of butterfly, pass through the same series of changes. . . Each animal is constrained to develop along definitely determined lines. The successive stages in its life history are forced on an animal in accordance with a law, the determination of which ranks as one of the greatest achievements of biological science." " 1 Man's Place in Nature, p. 88. Biological Lectures and Addresses, p. 201. |