The conception of disease as a product of a constitution is a heritage from antiquity, based on observation and experience.1 As is well known, the term constitution was originally used in a broad sense to denote a fixed or a prevailing state or condition. It was applied primarily to climatic and meteorological conditions, but was also used with reference to disease and to man.
To the ancient Greek, disease was a product of the interaction between man and his environment; still, environment was given first place, much as it is today, but for a different reason. The Greek regarded both man and disease as products of environment, while in recent years investigators have been inclined to disregard man and to stress the importance of a single environmental factor. This change of views is attributable to modern bacteriology. After centuries of abstract speculation concerning the cause of disease, bacteriology came like