541. As the result of these considerations, I approach alleged heteręsthesiae of various kinds with no presumption whatever against their real occurrence. Yet on the other hand, my belief in the extent of possible hyperoesthesia continually suggests to me that the apparently new perceptions may only consist of a mixture of familiar forms of perception, pushed to a new extreme, and centrally interpreted with a new acumen.

The conditions of experiment are by no means easy. I set aside, in the first place, a large number of experiments where there has been reason to think that the subject has followed, either fraudulently, or merely as the result of suggestion, the preconceived ideas of the experimenters. But more than this; self-suggestion on the subject's own part may be quite enough to make him translate some perception really gained in an old way into terms of some imagined new sensibility. Without presuming to criticise past evidence wholesale, I yet hope that the experience now attained may lead to a much greater number of well-guarded experiments in the near future. In a series of Appendices I very briefly present the actual state of this inquiry. In default of any logical principle, I shall there divide these alleged forms of sensibility according as they are excited by inorganic objects on the one hand, or by organisms (dead or living) on the other.

542. In the meantime I pass on to that group of the dynamogenic effects of suggestion which takes the next place in my scheme above indicated. I proceed from changes affecting the external senses to changes affecting the more central vital operations - either the vaso-motor system, or the neuro-muscular system, or the central sensory tracts. The effects of suggestion on character - induced changes to which we can hardly guess the nervous concomitant - will remain to be dealt with in yet another section.

First, then, as to the effects of suggestion on the vaso-motor system. Simple effects of this type form the commonest of" platform experiments." The mesmerist holds ammonia under his subject's nose, and tells him it is rose-water. The subject smells it eagerly, and his eyes do not water. The suggestion, that is to say, that the stinging vapour is inert has inhibited the vaso-motor reflexes which would ordinarily follow, and which no ordinary effort of will could restrain. Vice versā, when the subject smells rose-water, described as ammonia, he sneezes and his eyes water. These results, which his own will could not produce, follow on the mesmerist's word. No one who sees these simple tests applied can doubt the genuineness of the influence at work. We find then, as might be expected, that action on glands and secretions constitutes a large element in hypnotic therapeutics. The literature of suggestion is full of instances where a suppressed secretion has been restored at a previously arranged moment, almost with "astronomical punctuality." And yet in what memory is that command retained? by what signal is it announced ? or by what agency obeyed ?

In spite of this underlying obscurity, common to every branch of suggestion, these vaso-motor phenomena are by this time so familiar that a few references in my Appendices will suffice for their illustration.

543. This delicate responsiveness of the vaso-motor system has given rise to some curious spontaneous phenomena, and has suggested some experiments, which are probably as yet in their infancy. The main point of interest is that at this point spontaneous self-suggestion, and subsequently suggestion from without, have made a kind of first attempt at the modification of the human organism in what may be called fancy directions, - at the production of a change which has no therapeutic aim, and so to say, no physiological unity; but which is guided by an intellectual caprice along lines with which the organism is not previously familiar. I speak of the phenomenon commonly known as "stigmatisation," from the fact that its earliest spontaneous manifestations were suggested by imaginations brooding on the stigmata of Christ's passion; - the marks of wounds in hands and feet and side. This phenomenon, which was long treated both by savants and by devotees as though it must be either fraudulent or miraculous, - ou supercherie, ou miracle, - is now found (like a good many other phenomena previously deemed subject to that dilemma) to enter readily within the widening circuit of natural law.

Stigmatisation is, in fact, a form of vesication; and suggested vesication - with the quasi-burns and real blisters which obediently appear in any place and pattern that is ordered - is a high development of that same vaso-motor plasticity of which the ammonia-rose-water experiment was an early example (see cases in Appendices).

Equally striking, in a somewhat different direction, was Professor Charcot's production by suggestion of "blue oedema" (see 543 F), an experiment which, in itself a mere curiosity, was typical of a wide range of analogous effects which might in various states of the system prove actively beneficial.