led directly to the result as seen, but which have made no impression on the patient's memory. Still, it seems probable also that there may be mental influences excessively manifested over particular organs and functions, which are determined by purely subjective causes and without the intervention of external circumstance. Be that as it may, it seems to be necessary that there should be a certain preparation—a sort of condition precedent in the mind which makes it liable to abnormal manifestations. Mental influence over bodily function is in itself a constant and therefore a normal condition of existence. But one of the products of civilization is to exalt the mental into a too preponderating influence. In that exaltation the mind easily becomes hyper-susceptible. It takes on, with abnormal facility, a timbre of which it is not itself conscious, but which tends to modify biological relations in the way, among others, which I have to a certain extent illustrated in the preceding pages.
Now, there are various circumstances which favor modifications of psycho-biological relations, but which do not themselves directly cause them. Among those most frequently coming under professional recognition, hysteria may be instanced as a potent influence; but, in the light of the facts in my experience, it is incorrect to speak of the hysterical foot or the hysterical stomach or knee. We have the phenomena exhibited in both sexes, in children of tender years and in men and women in advanced life. Hysteria, or, more properly, imperfect sexual hygiene in both male and female, by perturbing the system, does produce a condition favoring modifications of the mental states; but the phenomena under consideration are not themselves hysterical. Any thing or any influence—and they are many—which can increase the mental tension and impressionability beyond a certain normal standard, will produce a modification of the timbre such as we see exemplified in so many instances. Besides the peculiar cases given as illustrations, there is a large class of what are called "simulated diseases," persons with local sensations or pains which do not arise from or represent corresponding local diseases. These can not have even a passing allusion here. Time also prevents me from entering into a discussion of the important subject of mental influence on actual disease, even if that aspect of my subject did not more properly belong to the medical department of biology Suffice it here to say that, as must be inferred from the facts and arguments already adduced, no system of therapeutics can be complete which does not embrace the design of controlling psycho-biological relations in general, and with reference to chronic disease especially.
From the foregoing presentation, several important and practical deductions may be drawn:
1. Mental culture, while it brings more physical pleasure, brings also increased bodily susceptibility.2. Pain, at least that which we are now considering, is but an in-