different receptor organs exists only in the higher animal; there are no specialised sense organs in a _Paramœcium_, for instance, and the whole periphery of the animal must receive all these different kinds of external stimuli at once. The specialisation of its receptor organs in the higher animal is rather the means whereby the organism becomes more receptive of its environment, than the means whereby it analyses that environment. This analysis is the work of the consciousness of the animal. [Illustration: FIG. 1.] Suppose that we draw a curve _AB_ freehand with a single undivided sweep of the pencil. By making a certain assumption--that the curve which we drew was one that might be regarded as cyclical, that is, might be repeated over and over again--we can subject it to harmonic analysis. We can decompose it into a number of other curves (_CD_, _EF_, etc.), each of which is a separate “wave” rising above and falling below the axis _OX_ in a symmetrical manner. If we draw any vertical line _MN_ cutting these curves, we shall find that the distance between the axis _OX_ and the main curve _AB_ is always equal to the algebraic sum of the distances between the axis and the other curves. These latter we call the harmonic constituents of the curve _AB_, supposing them to “add up” so as to form it. But _AB_ was something quite simple and elemental and its constituents cannot be said to have existed in it when we drew it freehand; it was only by an artifice of practical utility in mathematical computations that we _constructed_ them. It may be, of course, that the harmonic constituents of a curve had actual existence apart from the curve itself, but, in the case that we take, they certainly had not. Now we must think of our stream of consciousness in much the same way. It is something immediately experienced and elementary; it is the concomitant, if we choose so to regard it, of the external processes that go on outside our bodies. We can investigate it by thinking about it, and attending to one aspect of it after another, thus arbitrarily detaching one “part” of it from all the rest, but immediately we do this we rise above the flux of experience into the region of intellectual concepts. We have converted a multiplicity of states of consciousness, all of which co-exist along with each other, and in each other, and which have no spatial existence, into a multiplicity of states, visual, auditory, olfactory, etc., which have become separated from each other and have therefore acquired extension. This dissociation of the flux of experience is the process of conceptual analysis carried out by thought.