But if we recognise the brain as the organ of the mind, and give due weight to the complete distinctness and enormous superiority of the mind of man as compared with that of all other mammals, we shall be inclined to accept Owen's view as the most natural; and this becomes almost certain when we realise the enormous effect his mind has produced, in modifying and almost neutralising the action of that great law of natural selection which has held supreme sway in every other portion of the organic world. We have seen in the preceding chapter how every form of organic life during all the vast extent of geological time has been subject to the law of natural selection, which has incessantly moulded their bodily form and structure, external and internal, in strict adaptation to the successive changes of the world around them; while that world was itself hardly, if at all, modified by them. A few isolated cases—such as the formation of islands by the coral-forming zoophytes, or the damming of a few rivers by the rude though very remarkable labours of the beaver—can hardly be considered as forming exceptions to this law. But so soon as man appeared upon the earth, even in the earliest periods at which we have any proofs of his existence, or in the lowest state of barbarism in which we are now able to study him, we find him able to use and act upon the forces of Nature, and to modify his environment, both inorganic and organic, in ways which formed a completely new departure in the entire organic world. Among the very rudest of modern savages the wounded or the sick are assisted, at least with food and shelter, and often in other ways, so that they recover under circumstances that to most of the higher animals would be fatal. Neither does less robust health or vigour, or even the loss of a limb or of eyesight, necessarily entail death. The less fit are therefore not eliminated as among all other animals; and we behold, for the first time in the history of the world, the great law of natural selection by the survival only of "the fittest" to some extent neutralised. But this is only the first and least important of the effects produced by the superior faculties of man. In the whole animal world, as we have seen, every species is preserved in harmony with the slowly changing environment by modifications of its own organs or faculties, thus gradually leading to the production of new species equally adapted to the new environment as its ancestor was before the change occurred.