There is a great diversity of opinion concerning the etiologic factors of increased blood pressure and arteriosclerosis. The frequent association of the two conditions is granted. Which precedes the other, and what precedes both, have been matters of much study and debate. Five theories regarding the etiology of arteriosclerosis and hypertension may be considered: Mechanical-physical theory. A wearing out of the blood vessels as the result of the stress and strain of life. Chemical or infectious poisons theory. These may be exogenous, as from nicotine, or endogenous, as in chronic bacterial infections, diabetes, gout and nephritis. Metabolic theory. Poorly balanced diets with excess of protein or cholesterol; harmful but as yet undesignated end products of protein metabolism. Predisposition of certain groups of persons to degeneration of blood vessels theory. Disturbance of the acid-base balance theory. Such a disturbance in human subjects results from the continued eating of a diet