Page:Popular Science Monthly Volume 35.djvu/400

380 must have an important influence on the development of the brain, and hence also of the mind of which the brain is the organ.

Whatever differences of opinion may exist as to certain minor points in the physiology of the brain, all agree that it is organized on the same general plan as are the lower parts of the nervous system, and as are the entire nervous systems of those simple animals whose functions consist in feeble sensations which arouse equally feeble movements; and as there are no abrupt transitions either in the animal series or in individual development, so in the nervous system of man there is no abrupt introduction of mental conditions of a kind totally different from those which prevail at a lower plane of animal life, but rather the foundations of all mental processes are to be found in simple reflex actions. The mental building material is, therefore, derived from movements as well as from sensations; and a sensation and its associated movement may bo said to constitute the psychical unit of the whole mental life, as a sensory and motor nerve with their connecting center constitute the structural unit of the entire nervous system.

It is argued by Prof. Bain that it is by the experience of muscular exertion that we obtain our first real knowledge of the external world—a "not-me" as opposed to the "me" of passive sensation. Mr. Herbert Spencer also describes our fundamental conception of matter as of something which offers resistance. The different degrees of resistance met with from the "not-me" calling out different degrees of muscular effort, there arises a sense of discrimination which is the beginning of knowledge.

The duration of a muscular act also leaves its impression as a distinct element of consciousness; and the continuance of the mental state which accompanies this duration becomes a measure of time, the idea of which is thus incorporated in our mental make-up from the very dawn of consciousness.

The origin of the perception of space is similarly traced, in part at least, to movements; especially the idea of linear extension, which is greater or less in any given case according to the degree of contraction involved in moving the limbs through space, taken in connection with the time occupied. It is, then, largely by these fundamental modes of what may be termed muscular discrimination that we acquire our ideas of matter, of time and of space—the classic triad of "innate ideas" of the intuitionists. These supposed innate ideas being, however, susceptible of a psycho-physical explanation, we are bound by the law of parsimony to accept it.