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(15) The skin of the feet and legs is related to the pelvic organs. (16) The skin of the breasts is reflexly related to the pelvic organs. Two general classes of effects are produced by thermal and mechanical applications, The first is stimulating and tonic; the second, depressant and sedative. A stimulating effect is greater than a tonic effect, but both increase the vital activity. The intensity of the effect will be proportionate to the intensity of the application. On the other hand, depressant and sedative effects are both due to a decrease of activity. They differ in the extent of the decrease. Whatever the degree of reflex effect be, it is similar to the direct effect on the skin area treated. Four principal changes occur in the skin and the internal organs related to it. Try to remember them when treatments are given: (1) (2) (3) (4)
The blood vessels are contracted and remain so, as long as the application is in place, sometimes longer. The nerve sensibility is decreased. Glandular activity is decreased. The muscles contract firmly.
In healthy organs the vascular changes may not be excessively marked, but in congested or inflamed organs, these changes are often profound. Special reflex effects are seen with prolonged cold and differ from those caused by short applications of cold. Similarly, there are special effects from prolonged hot applications that differ somewhat from those of short duration. These are summarized in standard books on hydrotherapy. But before studying about the treatments and their indications, I will review some reflex principles involving generalized heat. All applications produce reflex effects. But applications of heat to a very large area dilate so many surface blood vessels that blood is withdrawn from internal or distant parts. Therefore, the reflex dilation of the blood vessels in this distant part is overcome, wiped out by the mechanical or hydrostatic effect. This is called derivation. Conversely, when cold is applied to a large area or the surface of the body is chilled, blood is driven from the outer parts. Then the internal blood vessels are filled and become dilated. Internal organ congestion results, called retrostasis. The above outline shows these different effects. Heat draws blood to the surface—derivation. Cold produces local vasoconstriction, driving blood to the interior—retrostasis. Then a secondary effect of cold draws blood to the surface again—derivation.