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Page:Popular Science Monthly Volume 4.djvu/345

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verse, that the industries of all the factories and trading establishments in the world are mere indolence, and awkwardness, and unproductiveness, compared to the miraculous activities of which his lazy bulk is the unheeding centre." Yet the conscious thought of the lout remains as unlike as possible to the conscious thought of the philosopher; nor will crusts of bread or bottles of wine educe aught from the lout's brain that men will think worth remembering in future ages.

Moreover, we must remember that we have to deal with facts, let the interpretation of these facts be what it may. The relations between mental activity and material processes affecting the substance of the brain are matters of observation and experiment. We may estimate the importance of such research with direct reference to the brain as the instrument of thought, without inquiring by what processes that instrument is called into action. "The piano which the master touches," to quote yet again from the philosophic pages of Holmes's "Mechanism in Thought and Morals," "must be as thoroughly understood as the musical box or clock which goes of itself by a spring or weight. A slight congestion or softening of the brain shows the least materialistic of philosophers that he must recognize the strict dependence of mind upon its organ in the only condition of life with which we are experimentally acquainted; and, what all recognize as soon as disease forces it upon their attention, all thinkers should recognize without waiting for such an irresistible demonstration. They should see that the study of the organ of thought, microscopically, chemically, experimentally, in the lower animals, in individuals and races, in health and in disease, in every aspect of external observation, as well as by internal consciousness, is just as necessary as if the mind were known to be nothing more than a function of the brain, in the same way as digestion is of the stomach."

In considering the growth of the mind, however, in these pages, it appears to me sufficient to call attention to the physical aspect of the subject, without entering into an account of what is known about the physical structure of the brain and the manner in which that structure is modified with advancing years. Moreover, I do not think it desirable, in the limited space available for such an essay as the present, to discuss the various forms of mental power; indeed, this is by no means essential where a general view of mental growth and decay is alone in question. Precisely as we can consider the development and decay of the bodily power without entering into a discussion of the various forms in which that power may be manifested, so we can discuss the growth of the mind without considering special forms of mental action.

Nevertheless, we cannot altogether avoid such considerations, simply because we must adopt some rule for determining what constitutes