I will therefore only say this: that the latest breeze from the physiological horizon need not necessarily be the most important one. Of the immense amount of work which the laboratories of Europe and America, and one may add of Asia and Australia, are producing every year, much is destined to speedy refutation; and of more it may be said that its interest is purely technical, and not in any degree philosophical or universal.
This being the case, I know you will justify me if I fall back on a doctrine which is fundamental and well established rather than novel, and ask you whether { 113} by taking counsel together we may not trace some new consequences from it which shall interest us all alike as men. I refer to the doctrine of reflex action, especially as extended to the brain. This is, of course, so familiar to you that I hardly need define it. In a general way, all educated people know what reflex action means.
It means that the acts we perform are always the result of outward discharges from the nervous centres, and that these outward discharges are themselves the result of impressions from the external world, carried in along one or another of our sensory nerves. Applied at first to only a portion of our acts, this conception has ended by being generalized more and more, so that now most physiologists tell us that every action whatever, even the most deliberately weighed and calculated, does, so far as its organic conditions go, follow the reflex type. There is not one which cannot be remotely, if not immediately, traced to an origin in some incoming impression of sense. There is no impression of sense which, unless inhibited by some other stronger one, does not immediately or remotely express itself in action of some kind. There is no one of those complicated performances in the convolutions of the brain to which our trains of thought correspond, which is not a mere middle term interposed between an incoming sensation that arouses it and an outgoing discharge of some sort, inhibitory if not exciting, to which itself gives rise. The structural unit of the nervous system is in fact a triad, neither of whose elements has any independent existence. The sensory impression exists only for the sake of awaking the central process of reflection, and the central process of reflection exists { 114} only for the sake of calling forth the final act. All action is thus _re_-action upon the outer world; and the middle stage of consideration or contemplation or thinking is only a place of transit, the bottom of a loop, both whose ends have their point of application in the outer world. If it should ever have no roots in the outer world, if it should ever happen that it led to no active measures, it would fail of its essential function, and would have to be considered either pathological or abortive. The current of life which runs in at our eyes or ears is meant to run out at our hands, feet, or lips. The only use of the thoughts it occasions while inside is to determine its direction to whichever of these organs shall, on the whole, under the circumstances actually present, act in the way most propitious to our welfare.