In Part I, the abnormal hydraulics of the circulatory system in the presence of an arteriovenous fistula was discussed and the following points emphasized: (1) An arteriovenous fistula introduces into the normal circulation consisting of heart-artery-capillary bed-vein, a second system of circulating blood consisting of heart-artery-fistula vein, the latter with a markedly diminished peripheral resistance; (2) the existence of four variable factors to maintain the normal circulation of blood at a definite blood pressure level, namely: (a) cardiac output or pulse rate, (b) total capacity of system as determined by contraction or dilatation of the vessel walls, (c) total volume of circulating blood, and (d) peripheral resistance. To compensate for the lowered peripheral resistance in the presence of a fistula, and to provide for the leakage of blood through the area of lowered resistance, thereby maintaining an adequate blood pressure level, an increase in total volume of circulating blood was