Civilized man has many diseases and infirmities in common with primitive man and the lower animals— accidents of birth, irregularities of adolescence and nutrition, cancer, infections and infectious diseases. On the other hand, there are certain diseases such as hyperthyroidism, neurocirculatory asthenia, peptic ulcer, diabetes and other less clearly defined diseases that are peculiarly the lot of civilized man. One should expect to find, then, that the mechanism the disturbance of which produces these diseases would be the mechanism on which civilized man's characteristics depend. The one characteristically human organ is the brain; the rise of the brain and its dominance has won for man his place in nature. It is characteristic of civilized man that his life is projected on rational lines, that it is full of work and worry as compared with that of the lower races of man and the lower animals. One would expect, therefore, that