Page:Popular Science Monthly Volume 5.djvu/433

Rh peculiarities in internal structure," has been shown by Mr. Spencer, and is indeed a corollary from the theory of development. Mr. Bain's method is therefore misleading from its contracted range, but we must here record, as part of our history, its very great advance on the still more incomplete methods of the older psychologists.

Mr. Bain's other contributions to Psychology are connected with the recent development of one of the sciences whose general method he appropriated. The physiology of the nervous system was of late foundation. Vesalius, Fallopius, Vieussens, Boerhaave, and Willis, had indeed assigned the special functions of certain organs (as those of the senses) to their appropriate nerves, but even in the middle of the eighteenth century the great Haller could deny the existence of any nerve which did not possess the double function of sensation and motion. Whytt and Prochaska, in 1768 and 1800, made observations on reflex and spontaneous movements, and decisively raised the question of the mode of action of the nervous system. In the first quarter of this century Sir Charles Bell established the existence of two great systems of nerves, with different functions, and thus revealed a definite mental mechanism. A few years later Dr. Marshall Hall (or some one else) discovered the independent action of the spinal cord, and helped further to determine the organic conditions of mental activity. His contemporary, Müller, went so far as to assert that the spinal cord was the centre or source of all motor power. At this point Mr. Bain came into the field. Appropriating the discovery of Hall, he was the first among psychologists to attempt systematically to elucidate the spontaneous movements, as no less a part of the phenomena of mind than those of consciousness. Combining Bell's discovery with a hint of Müller, he introduced the first organic modification into the association psychology by his theory of the brain as a fountain of force and not merely the passive instrument of impressions. This theory has led him, not only to take into account the secondary mental states generated by the bodily organs, but to trace genetically the origin and growth of voluntary power, and thus to constitute a separate department of Psychology by the analysis of volition, which had previously been the victim of introspection. It has also led him to devote a section to "constructive association," which could have no place so long as there was recognized in the mind no power of original construction. The tendency to materialize the mental agencies—the assumptions that nerve-force is of the nature of a current, that it moves in diffused waves, that associations are generated by shocks—are consequences partly of the introduction of the same new element. They are consequences also of that assumed correlation of the mental and nervous with the physical forces which Mr. Bain has, in his later editions, done much to prove and illustrate.

"If Mr. Herbert Spencer had no other titles to fame, he would