The servility, the state of fear of the subconscious, the source of neurosis, in its relation to the master hypnotizer is well brought out in the mechanism of hypnotic and post-hypnotic hallucinations.

Before we proceed with our discussion it may be well to give an analysis, however brief, of the normal percept, of the abnormal percept or hallucination, and then compare them with hypnotic and post-hypnotic hallucinations. The understanding of perception, normal and abnormal, is, in fact, at the basis of normal and abnormal psychology.

We may begin with the percept and its elements. In looking at the vase before me I see its beautiful tints, its rounded shape, its heavy pedestal with its rough curves, its solidity, weight, brittleness, and other experiences which go to make up the perception of the vase. The visual elements are given directly by the visual perceptive experience; but whence come the seemingly direct experiences of weight, heaviness, roughness, smoothness, and others of the like kind? They are evidently derived[251] from other senses. The whole perceptive experience is of a visual character. We take in the whole with our eye. In the organic structure of the percept then, besides the experiences directly given by the stimulated sense-organ, there are other experiences, sensory in character, indirectly given, and coming from other sense organs which are not directly stimulated.

The percept is a complicated dynamic product, and its elementary processes are never derived from one isolated domain of sensory experience. The activities of all the sensory domains co-operate in the total result of an apparently simple percept. Along with sensory processes directly stimulated, a mass of other sensory processes becomes organized and helps to contribute to the total result. The direct sensory elements are termed by me primary sensory elements; the indirectly given experiences are termed secondary sensory elements. The secondary sensory elements may be figuratively said to cluster round the primary sensory elements as their nucleus.

The whole perceptual experience is tinged by the character of the primary elements which constitute the guiding nucleus, so to say. Thus, where the primary sensory elements are visual, the whole mass, no matter from what domain the sensory experiences are derived, appears under the form of the visual[252] sense, and the percept is a visual percept. While the primary sensory elements form, so to say, the dynamic center of the total perceptual experience, the secondary sensory elements mainly constitute its content. Both primary and secondary elements are sensory and are induced peripherally; the primary directly, the secondary indirectly. The percept then is sensory and is constituted by primary sensory elements, or primary sensations, and by secondary sensory elements, or secondary sensations.

The character of the secondary sensory elements stands out clear and independent in the phenomena of synaesthesia, of secondary sensations. In the phenomena of synaesthesia we have a sensation of one sense organ followed, without an intermediary direct stimulation, by a sensation coming from another sense organ. Thus, when a sensation of light instead of giving rise to a subsequent idea gives rise to a sensation of sound, for instance, we have the phenomenon of secondary sensation. Here the secondary sensations stand out free and distinct, but they are really always present in our ordinary perceptive experiences as bound up secondary sensory elements, as secondary sensations grouped round primary sensations.

When the phenomena of synaesthesia were first brought to the notice of the scientific world, they were regarded as abnormal and exceptional, and only present in special pathological cases. Soon, however,[253] their field became widened, and they were found not only in the insane and degenerate, but in many persons otherwise perfectly normal. We find now that we must further widen the field of secondary sensory elements, and instead of regarding them as a freak of nature existing under highly artificial conditions, we must put them at the very foundation of the process of perception.

Secondary sensations are at the basis of perception. We have become so accustomed to them that we simply disregard them. When, however, the conditions change, when the secondary sensations stand out by themselves, isolated from the primary nuclear elements with which they are usually organically synthesized into a whole, into a percept, when they become dissociated, it is only then that we become conscious of them directly and declare them as abnormal.

Secondary sensations are always present in every act of perception; in fact, they form the main content of our perceptual activity, only we are not conscious of them, and it requires a special analysis to reveal them. Secondary sensations per se are not something abnormal—just as hydrogen present in the water we drink or the oxygen present in the air we breathe are not newly created elements,—it only requires an analysis to discover them. If there be any abnormality about secondary sensations, it is not in the elements themselves, but rather[254] in the fact of their dissociation from the primary............