We may define susceptibility primarily as the reaction of the organism to external and internal influences. While we may point out striking illustrations of susceptibility in the vegetable kingdom or among the lower animals, the best illustrations are to be found among those human beings with whom we come in contact.

We see very frequently the susceptibility to climatic

conditions, as well as all other phases of environment. One person will thrive in a rigorous climate where another will become seriously ill; one will thrive in dampness to which another would succumb. Altitude affects some individuals kindly and some adversely. The seashore improves one man's condition while it makes another man ill.

The power of assimilation and nutrition is one of the phases of susceptibility. One easily assimilates a certain kind of food while another finds the same food indigestible. "One man's meat is another man's poison."

Human beings are susceptible to infection and contagion in varying degrees. One man will become infected in contact with diseased individuals while another will experience no ill effects whatever. One person is made ill by noxious plants while another man can handle them with impunity. Certain people are capable of making a wonderful proving of a drug, whereas others will show no reaction whatever.

All these reactions have to do with susceptibility. Contagious diseases thrive in childhood because of the extreme susceptibility of the miasmatic influence; this susceptibility has an attractive force which draws to itself the disease which is on the same plane of vibration and which tends to correct this miasmatic deficiency. After having drawn to itself this other disease manifestation, the child becomes immune to further onslaughts of the same condition; his system has become somewhat cleared by this attraction of what Hahnemann calls a "similar disease" condition.

Susceptibility varies in degree in different patients, and at different times in the same patient. Homoeopathic application of a remedy is an illustration of meeting the susceptibility and filling the vacuum that is present in the sick individual. In other words, the vibrations of the sick individual call aloud for something to meet the need.

The proving of the remedy on a healthy individual gives us the basis of similarity of remedies to sick individuals because in a proving the remedy produces an artificial susceptibility similar to the susceptibility of the sick individual. The application of the homoeopathic remedy in sickness satisfies this natural susceptibility.

It is incumbent upon us to recognize, conserve and utilize normal susceptibility, to physical environments, to foods, to remedies and to toxic agencies. It should be our aim never to use any agent or anything of any nature, or to adopt any procedure, that would in the least diminish or destroy this power of susceptibility and the reaction of the organism in its normal manner. Upon this normal susceptibility and reaction depends the status of health.

To do anything to diminish or destroy the normal reaction is not the province of a physician; rather it is the province of the physician to conserve natural susceptibility, for without a recognition of this power all our efforts as physicians would be worthless. It is just as much the province of the physician to exercise conservation of susceptibility in the organism that it may act defensively against a toxin, contagion or infection, as it is to have this susceptibility react constructively to food and drink or to the curative remedy. Again, it is just as natural and important for the organism to react pathogenetically to the size and power of a dose of poison as it is for it to react to the demand for food.

Thus we see that susceptibility and reaction are basic principles, and are very closely allied to the problems of immunization. A proper concept of these principles is something that the homoeopathic physician must seriously consider; the interplay of these principles must become as second to him, if he wishes to use well the forces of nature in healing the sick.