With an increase in renal vein pressure by partial obstruction of the inferior vena cava in dogs, there follows an increase in thoracic lymph flow and a simultaneous decrease in urine flow and urine sodium excretion per minute. The increase in lymph flow appears to be caused by an increased production of renal lymph, since control animals with absent or nonfunctioning kidneys fail to show this lymph flow increase. Renal deviation of fluid and sodium to the lymphatics may similarly occur in heart failure and account for the retention of sodium and water.

A simple, rapid method for the bioassay of renin has been presented. Reliable and consistent results are obtained by this method whereby an arbitrary dog unit of renin has been established. The response of normal unanesthetized dogs to renin is independent of the body weight of dogs weighing between 10 and 25 kilos. An estimate of potency of renin per kilo of body weight of the test animals is therefore not only unnecessary but misleading. A dog unit of renin has been defined as that amount which raises the blood pressure at least 30 and not more than 35 mm. Hg within 3 minutes in at least three unanesthetized dogs. The potency is expressed as dog units of renin per cubic centimeter. The determination of the amount of renal substance represented by a cubic centimeter of extract and the number of dog units per cubic centimeter give an estimate of the yield of renin which can be expressed as dog units of renin per gram of original renal tissue. By determination of the number of dog units per cubic centimeter and the amount of nitrogen in milligrams per cubic centimeter in any renal extract the purity of the renin can be determined and expressed as dog units of renin per milligram N. The establishment of a standard method for the bioassay of renin is considered highly desirable and the method outlined in this paper is suggested for this purpose.

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Renal lymphatic pressure was found to be increased either by partial occlusion of the renal vein or total occlusion of the ureter. Simultaneous measurement of interstitial and lymphatic pressure revealed that with compression of the renal vein the rise in interstitial pressure preceded the rise in lymphatic pressure.

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