Page:Popular Science Monthly Volume 21.djvu/452

438 the farthest no other actions of the ganglion-cells in the nervous system of these animals are possible than those which serve their particular, instinctive actions. As the artisans from Newcastle-on-Tyne, at the Bureau of Emigration of New York, replied to the question what kind of work they understood, "Packing files," so animals with a perfected instinct purchase their superiority with a one-sidedness which, because they can learn no more, makes them appear as if they had never learned.

Susceptibility to exercise first enters into the animal world when the maintenance of the individual and the species has been so assured, through outer and inner circumstances, that the creature does not need a further particularly one-sided development. We are, then, free to conceive, with an appearance of justification, that the strength of the muscles employed in flight and digging, the thickened epidermis on the palms of the hands and the soles of the feet, the callus on the prehensile tail and the buttocks of apes, the bone-prominences at the attachments of the muscles, and many other similar things, depend on the inherited consequences of nutritive and formative stimulation, while the most diversified kinds of skill may be traced back to inherited concatenations of actions of the ganglion-cells; and this, whether we consider the waves which flow along apparently in a purely mechanical manner in the gymnotus-fin, or in the thousand feet of the woodlouse; or the intelligent posture of the French pointer, which, untaught, and without ever having seen one before, points at the lizard in the sub-tropical shrubbery as his ancestors pointed at the partridge on the plain of St. Denis. With Mr. Herbert Spencer meeting me in the same thought, which I believe, however, I have more sharply grasped, I deduced on a former occasion how, in such transmissibility of educationally derived aptitudes, possibly lies the reconciliation of the great antitheses of the theory of knowledge—of the empirical and the innate views.

Besides improvement by exercise, improvement by natural selection should not be left out of the account, if we would understand the adaptability of organic nature, for a threefold reason: First, there are numerous adaptations—I mean only the so-called sympathetic colorings—for which natural selection, not exercise, seems to afford an explanation. Secondly, plants, which are not less adaptable in their way than animals, do not enjoy exercise. A few phenomena of plant life, reminding us of callus, and traceable back to nutritive and formative stimulation, belong rather to the region of healing and restoration, which is at this point closely connected with exercise. Thirdly, and finally, we require natural selection in order to explain the origin of the adaptability to exercise itself.

Indeed, the usefulness of exercise in its most diversified forms is in itself a deep problem. If we do not concede, as we can not scientifically, that the adaptive quality originated otherwise than