a sudden fit of anger makes a mother's milk poisonous to her child.
In general, an emotional storm or even an emotional mood, if long continued, may have a profound effect upon the functioning of the body. The cheerful emotions favor health; the depressing emotions make the body fertile ground for the growth of disease germs. Yet even this admission does not bring one much nearer the point of interest; for, since the epoch-making discoveries of Prof. James, of Harvard, and Prof. Lange, of Copenhagen, it has been known that what we call an emotion is not the cause but the feeling of those extensive bodily changes which we regard as its expression, and to inquire into the effect of emotions upon metabolism would lead me too far afield into the general theory of emotion.
To account for the more remarkable effects of suggestion upon metabolism we are forced to a most extraordinary hypothesis, which may be thus stated:
The thought of any given bodily change, whether motor, vasomotor, or metabolic, tends to the actual production in the body of the change which that thought represents.
That this law is true of motor thoughts I think quite clearly proved. Of the vasomotor it is not so clearly true, but there is a considerable amount of evidence going to show that the blood tide can be to some extent directed by act of will by most persons, and by some persons to a much greater extent. The evidence for any control over the metabolic processes is very scanty. If the tendency exists, it must be latent in most persons, for we all know that I can not by thinking add a cubit to my stature or change the color of my beard. Yet, even though it be latent in most persons, it may exist in others, and I think the evidence for its existence is strong. The chief difficulty in accepting it lies in this: we know of no nervous mechanism by which such central processes can affect the body unless it be through the sensory nerves, and, according to our present physiology, sensory nerves can carry impulses in one direction only.
I can not explain these difficulties and shall not attempt to. I shall simply relate the more important bits of evidence which have been gathered since the 12th of May, 1885, when M. Focachon performed his first successful experiment under satisfactory conditions before the professors of the Medical School at Nancy. Most of this evidence is experimental and it deals with modifications of the skin only. I do not suppose that this fact proves that the control of thought over the skin is greater than that which it exercises over the internal organs, but merely that experiments
- Carpenter, Mental Physiology, § 566.