That vascular tension is an important factor in the mechanism of the toxemias of pregnancy was postulated many years ago. Cohnheim,1 in 1880, seems to have been the first to express the view that albuninuria and anuria in eclampsia might be due to a spasm of the renal vessels. In 1918, Volhard2 advanced the hypothesis that a generalized arterial spasm accounted for the hypertension, convulsions and renal symptoms in eclampsia. Heynemann3 also assumed that a general arterial spasm produced the symptoms. Various attempts to demonstrate vascular spasm have been more or less successful. Hinselmann4 (1924) noted the capillary changes in the finger-nail beds. He assumed that the capillary stasis and the dilatation were secondary to an arteriolar spasm. Subsequent observations of the nicking of retinal arteries and veins and the beading and the contractions of these vessels have indicated that the vascular spasm is probably general.