62. These organs are situated upon the sides of the vertebral column, just before the last false ribs. From their oblong figure, they have been compared in shape to large beans. The right kidney lies under the left lobe of the liver, and is consequently lower than the left, which lies under the spleen. Their volume is small when compared with the large quantity of fluid which they secrete; and it appears probable, that the chemical functions which they perform are less extensive than those which may be regarded as more strictly mechanical. They are generally surrounded with a considerable quantity of fat: their parenchyma is composed of two substances; the one exterior, vascular, or cortical; the other, called tubular, disposed in a certain number of cones, the bases of which correspond to the surface of the organ, while their summits unite in the membranous cavity called pelvis. These cones appear to be formed by a great number of small hollow fibres, which are excretory canals of a particular kind, and which are generally filled with urine.

It is a curious fact, that if a slight compression be made upon these uriniferous cones, the urine will pass out in considerable quantity; but, instead of being limpid, as when it passes out naturally, it is muddy and thick, which evidently proves that the hollow fibres act as filters. In respect to its volume, no organ receives so much blood as the kidney: the artery which is directed there is large, short, and proceeds immediately from the aorta. Haller has decided, that no less than a thousand ounces of blood may pass through the renal structure in the space of an hour; and the extreme facility with which the coarsest injections pass through the renal arteries into the ureters, or excretory ducts, affords a convincing proof of the immediate connexion which exists between all the different parts of the structure of the kidney. The filaments of the great sympathetic are alone distributed to these organs.