Page:Popular Science Monthly Volume 46.djvu/824

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forehead of Jove. They are the children of a slower evolution. Each organ performs its function so perfectly because of the discipline of use, because of the slow discipline of long-continued use. We recognize this in the matter of the actions called physical. We build gymnasiums on this principle, and lay out our athletic grounds accordingly. The runner wants well-developed nerve and muscle, and he wants the habit of rapid action. The champion in every sport needs the human apparatus, the nerve and sinew, and he also needs the habit of prompt exercise. It is the same with the bodily organs and functions. Strong lungs come from deep breathing and the pumping of maximum quantities of air. If we want a strong stomach we must give it work to do. We must eat cheese and nuts and other foods that are hard to digest. It will never do to live on peptones. All this is very obvious. But it is less obvious when we come to speak of the operations of the spirit. Yet the case is quite the same. We need the organ and, through exercise, the well-developed function. Our thinking is connected with molecular changes in the brain and spinal column. It will depend upon these and upon the degree of their organization. But thinking is a complex operation. It may be resolved into simpler elements, into sensations. But even here it no longer suffices to say that these sensations are transmitted to the brain. This language is entirely too general. Their destination may be specifically stated. They go to a particular part of the brain, depending on their nature.

With respect to the outer world, we have but one sense, and that is the sense of touch. All our impressions are tactile. The outer world has for us but one mode of operation, and that is through motion. The organs of sense are attuned to different degrees of motion, and unerringly pick out their own notes. The ear, sensitive enough to the coarse air waves which constitute sound, is utterly deaf to the minute light waves which so easily affect the eye. The ego touches the outer world only at its own bodily extremities. What it comes in contact with is motion. For us, then, the outer world is coextensive with motion, and with only so much motion as we can perceive. The outer world has different dimensions according to the sensitiveness of this power of perception. The motion to which we do not respond is an unseen and unknown world—an undiscovered country. The motion to which we do respond makes up our entire world. It is our universe.

The impressions gathered by the several senses are transmitted to the brain over their appropriate nerve routes. Here at this central station the same exquisite division of labor prevails as at the outlying stations on the circumference. In receiving sensa-