Page:Proceedings of the Royal Society of London Vol 4.djvu/401

Rh vatory, Ross-Bank, Van Diemen's Land, for April, May and June 1841." (Forms 1 & 2.)

5. The reading of a paper, entitled, " On the Structure and Use of the Malpighian bodies of the Kidney, with Observations on the Cir- culation through that Gland." By William Bowman, Esq., F.R.S., Demonstrator of Anatomy in King's College, London, and Assistant Surgeon to the King's College Hospital, was resumed and con- cluded.

The author describes the results of his examination of the struc- ture and connexions of the Malpighian bodies of the kidney in dif- ferent tribes of Vertebrata, and shows that they consist essentially of a small mass of vessels, contained within dilated extremities of the convoluted uriniferous tubes. The tubes themselves consist of an outer transparent membrane (termed by the author the basement membrane) lined by epithelium. This basement membrane, where it is expanded over the tuft of vessels, constitutes the capsule de- scribed by Miiller. The epithelium lining the uriniferous tube is altered in its character where the tube is continuous with the cap- sule, being there more transparent, and furnished with cilia, which, in the frog, may be seen, for many hours after death, in very active motion, directing a current down the tube. Farther within the cap- sule the epithelium is excessively delicate, and even, in many cases, absent. The renal artery, with the exception of a few branches given off to the capsule, surrounding fat, and coats of the larger blood- vessels, divides itself into minute twigs, which are the afferent ves- sels of the Malpighian tufts. After it has pierced the capsule, the twig dilates, and suddenly divides and subdivides itself into several minute branches, terminating in convoluted capillaries, which are collected in the form of a ball ; and from the interior of the ball the solitary efferent vessel emerges, passing out of the capsule by the side of the single afferent vessel. This ball lies loose and bare in the capsule, being attached to it only by its afferent and efferent ves- sel ; and is divided into as many lobes as there are primary subdivi- sions of the afferent vessel ; and every vessel composing it is bare and uncovered, an arrangement of which the economy presents no other example. The efferent vessels, on leaving the Malpighian bodies, enter separately the plexus of capillaries surrounding the uriniferous tubes, and supply that plexus with blood. The blood of the vasa vasorum also probably enters this plexus. The plexus itself lies on the outside of the tubes, on the deep surface of the membrane which furnishes the secretion ; and from it the renal vein arises by nume- rous radicles.

Thus the blood, in its course through the kidney, passes through two distinct systems of capillary vessels ; first, through that within the extremities of the uriniferous tubes ; and secondly, through that on the exterior of these tubes. The author points out striking dif- ferences between these two systems. He also describes collectively