Page:Proceedings of the Royal Society of London Vol 4.djvu/402

Rh under the name of Portal System of the Kidney, all the solitary ef- ferent vessels of the Malpighian bodies, and compares them with the portal system of the liver ; both serving to convey blood between two capillary systems. In the latter, a trunk is formed merely for the convenience of transport, the two systems it connects being far apart. But a portion even of this has no venous trunk, viz. that furnished by the capillaries of the hepatic artery throughout the liver, which pour themselves either into the terminal branches of the portal vein, or else directly into the portal-hepatic capillary plexus. On the other hand, in the kidney, the efferent vessels of the Malpighian bodies, situated near the medullary cones, having to supply the plexus of the cones, which is at some little distance, are often large, and divide themselves after the manner of an artery. They are portal veins in miniature. In further confirmation of his view of the existence of a true portal system in the kidney of the higher orders of animals, where it has never hitherto been suspected, the author describes his observations on the circulation through the kidney of the Boa Con- strictor, an animal which affords a good example of those in which portal blood derived from the hinder part of the body traverses the kidney. He shows that here the Malpighian bodies are sup- plied, as elsewhere, by the artery, and that their efferent vessels are radicles of the vena portse within the organ, and join its branches as they are dividing to form the plexus surrounding the tubes ; thus corresponding with the hepatic origin of the great vena portae. In other words, the vena portse is an appendage to the efferent vessels of the Malpighian bodies, and aids them in supplying blood to the plexus of the tubes. Thus in this variety of the kidney, as in the liver, there is an internal as well as an external origin of the portal system; while in the kidney of the higher animals, this system has only an internal or renal origin, viz. that from the Malpighian bodies.

A detail of the results of injection by the arteries, veins and ducts is then given, and they are shown to accord with the preceding de- scription. Many varieties in the Malpighian bodies in different ani- mals are also pointed out, especially as regards their size.

The author then proceeds to found on his previous observations, and on other grounds, a theory of a double function of the kidney. He conceives that the aqueous portion of the secretion is furnished by the Malpighian bodies, and its characteristic proximate princi- ples by the walls of the tubes. After giving in detail his reasons for entertaining this view, he concludes by referring to the striking analogy between the liver and kidney both in structure and func- tion, and by expressing his belief, first, that diuretic medicines act specially on the Malpighian bodies, and that many substances, espe- cially salts, which when taken into the system have a tendency to pass off by the kidneys with rapidity, in reality escape through the Malpighian bodies; secondly, that certain morbid products occa- sionally found in the urine, such as sugar, albumen, and the red par- ticles of the blood, also, in all probability, pass off through this baife system of capillaries.