DEMONSTRATION OF THE NATURE OF THE ARTERIO-VENOUS MESHWORK IN THE FROG'S KIDNEY

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Abstract
The author considers Nussbaum''s concept that there is a double circulation and a double capillary bed in the kidney of the frog, and Woodland''s idea that the blood from the renal portal vein does not supply the kidney but passes through in relatively large channels with little or no functional relation to the kidney. The aorta, post caval vein, and renal portal veins were cannulated in bullfrogs (Rana catesbiana) and a count of the drop rate from the post caval vein cannula was made. Injections of adrenalin into either system caused decrease in drop rate, but in all cases the decrease was greater when injection was made into the arterial system than when made into the vein. Histamin caused increase of drop rate when injected in the artery and decrease when injected in the vein. Air injected in the artery did not pass through the kidney but when injected into the vein it was seen passing through in several rather large channels. Hg gave the same results, and Paramoecia came through these channels very readily, but would not pass through if injection was made in the artery. By transillumination of the kidney, channels from the renal portal vein were easily traced through the kidney, and the observation was made that anastomosis between them and the capillary bed was very complete. Blood flowed normally from the capillary bed into the channels, but if pressure were placed on the renal arteries the flow was reversed. Thus either system of blood vessels could be ligated and the kidney still function normally. Frogs and toads with either the renal arteries or renal portal veins ligated lived as long as controls similarly operated upon but without ligation of blood vessels. It is concluded that perfusion experiments founded on the idea that the occlusion of either set of blood vessels to the kidney causes a cessation of function of any part of the kidney are without basis, and that while there are channels through the kidney from the renal portal vein the anastomosis is so complete that the entire kidney will be supplied with blood from this source whenever the arterial pressure drops.

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