LOCALIZATION OF FUNCTION IN THE BRAIN.
(Plate XI.) From the facts which have been explained it will be understood what is meant by the phrase localization of function in brain and spinal cord. The brain and spinal cord do not act as a whole in the multitudinous variety of nerve operations. One part of the brain or spinal cord—one group of nerve-cells—is set apart for one duty, another group for another duty, so that a particular function is limited to a par ticular group or groups of nerve-cells—the function is localized.
These modern views of the localization of function in small areas of nervous substance are fitted to rouse grave reflections. We know that it is true of a muscle that moderate and regular exercise of it conduces to its increased development and power. It is by constant exercise that the arms of those accustomed to manual labour are so strong and well formed. Further, we know that want of use causes a muscle to waste. An arm put up in splints for six weeks for fracture is much thinner than its neighbour at the end of that time, just because of its enforced idleness. Proper use increases strength, want of use weakens. There is no manlier of doubt that these rules apply to the nervous system. Everybody knows that a man who regularly studies music becomes by and by more or less of an adept at his art; every body knows that the man who fitfully studies anything shows evident signs of his neglect. Now the application of these rules to what has been said about special centres in the brain means that the systematic use of any faculty of the mind develops and strengthens the nerve-centre that presides over that faculty, and that disuse means waste of the nerve centres. Thus, to put it broadly, a man may be supposed to be born with a brain that may be thought of as a series of nerve-centres ; these various centres have the capacity of being trained to discharge certain duties; if the train ing be given, the centres will be developed, and the man will be able to perform the duty; if the centres be not trained they will degenerate and decay, and the man will be unable to per form the duty. People excuse themselves for
defects of education, or other defects, by say ing, "I have no head for this," "I have no faculty for that." This translated into stricter language would be, "I neglected to develop the capacity I once possessed, and it, conse quently, has gone to waste." The time for developing nerve-centres, for training or educating them, is naturally during the period when growth is possible, that is; in youth.
For if the nerve-centres are not exercised during the growing period, their development will not take place ; and when the growing period is passed the risk of development being impossible is great.
A word of caution is necessary. While what has been said is an argument for an all-round training, a training of eye and ear, tongue and hand—training of every muscle of the body as well as of every faculty of the mind,—it must not be taken to sanction overburdening and overstraining of nerve-centres. The runner training for a race does not begin at once to go at full speed for his full distance. He takes short distances at first and leisurely to accustom his muscles to their work, and he gradually goes farther and faster, always avoiding ex haustion. So the training from the youth up should be prudent and regulated with a watchful care against over-work. For over exertion and over-stimulation are as ruinous as neglect.
view that certain little areas of brain substance are connected with certain functions is not to be confounded with phrenology, which maps out on the outside of the skull certain regions said to be devoted to certain emotions, &c., the prominence of the regions indicating the amount of development of the faculty, emotion, &c. The brain exhibits no such divisions as phrenology creates, still less can any prominence or depression on the outside of the head indicate, through scalp and bones, the shape of that part of the brain with in. The phrenological theory was first pro pounded by Gall and Spurzheim in the begin ning of the past century.