The pathogenesis of edema of renal origin is concerned with changes in the blood, vessels and tissues. A review of the literature on the subject is confusing and unsatisfactory. Bright asserted that the depletion of albumin in the blood changed the physicochemical balance and edema resulted. Later Senator suggested the vascular element, and in recent years Fischer has implicated the tissue cells in the genesis of edema. The part played by the blood has interested many observers, but the exact significance of its volume in this connection has not been clear. The following brief excerpts from Loeb's1 review of the subject of edema depict the prevailing confusion: Volhard2 stated that in acute glomerular nephritis with edema there is no dilution of the blood, while without edema there may be dilution. In the latter, because of the renal block, water is retained in the blood; in the former, water and salts,