14 PSYCHOTHERAPY : SCIENTIFIC AND RELIGIOUS chap.
known regarding these families the high percentages reported in these statistical studies might not be so imposing.
It has been stated that mental illness tends to disappear in three generations and that with each succeeding generation the illness appears earlier in life. This may be due to the earlier recognition and hospital treatment of the illness, and therefore to the lesser chance of reproduction, especially in the case of schizophrenic patients.
To revert to the influence of environment, let it be assumed that any part of the external world to which a human being is responsive may operate on his inherited aptitudes. Ordinary environment means the totality of external forces, infinitely variable and complex, which begin to act upon an individual even before birth. For scientific purposes such a conception is inadequate. Biological studies of the development of lower animals have extended the problem of heredity and environment to the time of conception. It has been found that the new organism is actually the result of the constant interaction of the genes and the surrounding cytoplasm. The action of any particular gene varies widely and is dependent upon the hormones in the surrounding medium. Moreover, some of the genes do not come into action until after the fundamental structures of organs have been developed. In the course of embryonic development each cell is constantly being modified by the needs of adjacent cells. Organs are likewise exerting an influence on each other's growth. In other words, each cell and each organ has its own environment which is constantly changing during the process of growth.
It appears, therefore, that the contributions of heredity are subject to change from the very beginning of life. We might wonder, then, to what extent the health and