GENERAL CONTROLS OF CONDUCT 9
and most notably in man, runs an increase in the complex ity of the nervous organization, which is truly wonderful in the brute world, but in man, and especially in highly de veloped men, becomes phenomenal. If we think of a nerve as a line along which a stimulus is transmitted, the highly complex nervous organization of a cultured man presents a system of such lines all but infinite in its intricacy, com prehending subordinate and sub-subordinate systems, and all so inter-related that a stimulation affecting any part of it will spread to larger and larger areas, according to the de gree of its intensity and to the general condition of the or ganism; and it often radiates along these myriad paths of conduction until it involves the whole system. This in crease in complexity of nervous organization is the physical basis of a corresponding increase in the number of possible reactions upon the environment. In a simple reflex act there is just the one reaction possible. In a purely in stinctive action the reaction is more complex than in the re flex, but there is still no alternative. But with the increase of the complexity of the nervous organization the organ ism more and more acquires the power to retain and revive the impressions made by past reactions and to utilize them in some measure in making subsequent responses. At the same time the various sensory areas become linked up to gether. Thus with the power to retain and revive past im pressions and the linking together of the several sense cen tres, it becomes possible for the organism to react in sev eral different ways to the same stimulus ; and it is not only possible, there is a tendency for it to do so. Naturally these tendencies often conflict with one another, and some means of resolving the conflict is needed. It is just here that consciousness makes its appearance. These conflicting motor tendencies create a general tension in the organism, which, as we shall see, is the physical basis of feeling; and the means of resolving the conflict is the revival of past im pressions, which always appear as mental images; and these, as we shall see, constitute the elements of the intel-
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