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Show MR. W. WOODLAND ON TJ1E [Nov. 27, It is also exceedingly probable that the completely median position of the primitive posterior cardinals in the region of the kidneys in mammals, is due to the absence of encroachment upon the lumen of the veins by the kidneys. Recapitulation and Conclusion. To recapitulate the entire argument: In view of the fact that the supply of arterial blood to the kidneys is only partial and does not involve the whole aorta (the inference from this being that a venous supply is unnecessary), and of the further facts that the renal cardinal meshwork is not found in those animals which most require it, and that in those animals in which it is found at least half the blood avoids its passage; seeing that when the meshwork is absent there is no diminution in volume of the kidney, and that the meshwork is radically different in regard to its mode of origin as compared with the true portal system of the liver ; seeing that the venous " portal capillaries " of the kidney are too large to be properly denoted by that term, and that, unlike the hepatic-portal system, the walls of the kidney " capillaries ' contain 110 muscles and are devoid of a nervous supply, there is every reason to believe on a priori grounds that the renal cardinal meshwork is not excretory in nature. posteriori evidence in confirmation of this conclusion has also been supplied, as we have seen, by the results of certain physiological experiments, some of which, though not conducted in as satisfactory a manner as could be wished from the present standpoint, yet were probably sufficiently well performed to justify reference to them. If the renal cardinal meshwork is thus not excretory in nature, then, it being extremely improbable that the meshwork possesses some other function, it follows that the association of the kidney and vein is probably functionless. If functionless, it is on this account certain that the meshwork is accidental in origin-a byproduct having no relation to the animal economy-and I have supplied a certain amount of evidence to this effect. In short, I have endeavoured to show that the renal cardinal meshwork is simply an instance of the extension of a growing organ in the direction of least resistance; in other words, a mechanical product bearing 110 direct relation to the physiological needs of the animal. In conclusion I wish to express my indebtedness to Dr. Ridewood, who very kindly read through the manuscript and offered several suggestions, and to Professor Starling, who kindly assisted me in connection with the literature of the subject. A p p e n d ix . On the Production of Pelvic Veins; i. e., an additional sub-abdom inal communication between the iliac and caudal veins and the heart. Several reasons have been given in the paper referred to in the text (10) to account for the return to the heart of the venous |