HEREDITY

plays an important role in the causation and the prevention of disease. In most cascs the discase itself is not inherited, but the tendency to it is. A constitution with only a low resisting power to the invasion of certain germs is often transmitted, and the offspring, when exposed to infection later in lifo, then take the disease. Similarly a constitution with a ae resisting power may be transmitted to the offspring, who then escape the disease though often exposed to infection. Hence we have some families prone to consumption, others to cancer, and again some races prone to a disease, whilst other races living at the same spot escape. For instance, plague attacks the blacks far more frequently than the whites. Just as we have certain constitutions that offer @ suitable soil for certain disease so we have inherited constitutions liable to become pee in one peruouiee way; for instance, gout, diabetes, and insanity frequently run in families. In these cases it is the tendency and not the disease which is inherited, and by strict attention to the laws of health harm may be avoided as a rule, Tho unstable nervous system of those with insanity in the family break down under the stre of many causes, ¢.g. overwork, anxiety, alcohol, acute bodily discase, or ehild-birth, and insanity or hysteria result. Hence tho regulation of the life by medical guidance in such cases is most desirable. [s. 373]