Mental Influence on Organs.—The Heart.—The influence of mind can be noted on practically every organ of the body in a concrete way. It might be thought that the heart, the first living thing in the animal being, the pulsations of which begin before there is any sign of the nervous system, might be free from this influence. On the contrary, the heart is so readily affected by mental states that, taking effect for cause, the old popular, and even scientific idea with regard to it, was that it was the organ of the emotions. The heart is stimulated more by favoring circumstances, and suffers more from depression, than almost any other organ. In the melancholic states it usually beats less frequently and is sluggish. When individuals are tired out and the heart has become weakened in its action, new courage will first be noted as having its effect upon the heart action. As the whole muscular system is much influenced by the mental state and, as the control of the arterial system depends on the muscles in the arteries, it is easy to understand how much the general bodily condition may by mental influence be modified for good and ill.
Digestive Tract .—The stomach and intestines, though their functions might be presumed to be dependent entirely on physical conditions, are almost completely under the control of the mental state. At moments of depression, just after bad news has been received, the appetite is absent, or is very slight and digestion itself proceeds slowly and unsatisfactorily. On the other hand, when there is mental good feeling appetite is vigorous and digestion is usually quite capable of disposing of all that is eaten. If after a period of rejoicing in the midst of which food is taken abundantly bad news is brought, the mental influence on digestion can be seen very well. It is not alone that depression interferes with digestive processes, but apparently some favorable factors for digestion consequent upon the previous state of mind are withdrawn, and now what would have been a proper amount of food proves to be an excess and the digestive organs find it difficult to deal with it.
Nervous Inhibition.—The mind can actually inhibit certain of the involuntary processes of the body by thinking about them, and, above all, by dwelling on the thought that they are going wrong. This becomes easier to understand when we recall how, in the same way, we may disturb many habitual and more or less unconscious actions that we have grown accustomed to. There are any number of actions requiring careful attention to details which become so habitual that we do not have to think of them at all. Not infrequently it happens when we try to explain to others how we do them, we disturb the facility of performance and have to repeat the acts several times before we succeed in performing successfully what a moment before we did without any thought. The story of the centipede who was asked how he walked with all his hundred legs, and who tried to describe how easy it was and got so mixed up that he was unable to move at all, is a whimsical symbol of conscious attention disturbing actions which go on quite well of themselves if only we do not allow ourselves to think consciously of each and every phase of them.
How much the mind may influence the body under certain conditions when trance-like states either assert themselves or are brought on, has often been noted. Lombroso in his book "After Death What?"10 says of Eusapia Paladino the "medium," that "when she is about to enter the trance state the frequency of the respiratory movements is lessened just as is the case with the Indian fakirs. Before the trance she will have been breathing eighteen to twenty times a minute; as the trance begins the number of respirations is gradually reduced to fifteen; when the trance is fully developed she breathes twelve times a minute or less. On the other hand, at the same time the heart beats increase. Normally her pulse is about seventy, but during the early trance stage it rises to ninety, while during the course of a deep trance, it may go as high even as one hundred and twenty. The passing from a more or less rigid state to that of active somnambulism is marked by yawns and sobs and spontaneous perspiration on the forehead." The observation of these phenomena is, of course, entirely apart from any theory one may hold with regard to mediumistic manifestations, and it provides evidence of mental influence that is very striking.
Imaginary Drug Effects.—Drug effects may be produced through the imagination. Physicians know that when patients are persuaded that certain effects are to be expected from a particular medicine, the effects may follow all the same in sensitive, imaginative people, if that medicine is replaced by some inert compound. Many a physician who has used bread pills or other placebos to replace a drug that he did not want the patient to acquire a habit for, has thus been able to allow good effects to go on without interruption, where the stoppage of medicine had previously interfered with the continuance of the good habit that had been formed. Very few physicians have not seen the effect of a hypodermic of pure water when a hypodermic of morphine is demanded, and when the patient would not sleep without having the hypodermic injection. Sleeping powders of various kinds can sometimes with distinct advantage be replaced by inert materials, because the patient's mind is fixed upon the idea of sleep coming after a certain time and they, in consequence, compose themselves to rest.
The Nerves and Tissues.—Cases occur where disturbances of vitality are noted as a consequence of nervous affections, though no gross lesion of the nervous system is demonstrated. Certain nervous people suffer from ulcerative conditions of their hands, and it is evident that in some the nervous impulses that would ordinarily keep the skin surface in good, healthy condition are insufficient. Some people who use a typewriter have no difficulty at all with the ends of their fingers, while others are subject even to loss of skin or ulcerative conditions that make it almost impossible for them to go on with their work. In some this is true in the winter, in others in the summer. There are a number of skin conditions which are due to nervous factors and these evidently point to the influence of the central nervous system in keeping the forces of our body in such health, and resistive vitality, as will enable us to carry on whatever work we may wish to. This is, of course, a very individual matter. Some people chap very easily, some suffer from chilblains, or are frost-bitten even on slight exposure, and these peculiarities are evidently dependent on the intensity of the nervous impulses as well as the tone of the circulation, which itself depends on the nerves to a great extent.
It is evident that some of these disturbances are not enduring, but are only temporary and therefore are due to functional disturbances of the nervous system. Physicians often see hysterical patients suffering from intense pain that requires an injection of morphine, yet after a series of such incidents, the physician is able to give an injection of plain water and produce just as good an anodyne effect. In these cases some influence of the will is enough to correct the painful disturbances. Occasionally a single member loses sensation, or motion, or both, yet the fact that its nutrition does not suffer shows that there is only disturbance in the motor connections between it and the central nervous system and not in the sensory nor trophic tracts, and that this functional defect may be restored by some favorable influence.
Nerve Supply and Health .—We know now that when a part of the body is cut off from its connections with the central nervous system, it begins at once to be lowered in vitality and gradually tends to dissolution. This will be true in spite of the fact that the circulation continues as actively as before. It is not necessary, indeed, that the nerve trunk to a part should be cut, if it is sufficiently compressed its function is stopped and various disturbances begin to appear in the vitality of the part which it supplies. A typical example is to be seen in certain fractures of the clavicle, where a fragment presses on one of the nerves leading to the arm. After a time