As he released the clamp which held the artery, the little dog’s feverishly beating heart spurted the arterial blood from the carotid into the tubes holding the normal salt solution and that pressure, in turn, pumped the salt solution which filled the tubes into the jugular vein, thus replacing the arterial blood that had poured into the tubes from the other end and maintaining the normal hydrostatic conditions in the body circulation.  The dog was being kept alive, although perhaps a third of his blood was out of his body.

“You see,” he said at length, after we had watched the process a few minutes, “what I have here is in reality an artificial kidney.  It is a system that has been devised by several doctors at Johns Hopkins.

“If there is any toxin in the blood of this dog, the kidneys are naturally endeavoring to eliminate it.  Perhaps it is being eliminated too slowly.  In that case this arrangement which I have here will aid them.  We call it vividiffusion and it depends for its action on the physical principle of osmosis, the passage of substances of a certain kind through a porous membrane, such as these tubes of celloidin.

“Thus any substance, any poison that is dialyzable is diffused into the surrounding salt solution and the blood is passed back into the body, with no air in it, no infection, and without alteration.  Clotting is prevented by the injection of a harmless substance derived from leeches, known as hirudin.  I prevent the loss of anything in the blood which I want retained by placing in the salt solution around the tubes an amount of that substance equal to that held in solution by the blood.  Of course that does not apply to the colloidal substances in the blood which would not pass by osmosis under any circumstances.  But by such adjustments I can remove and study any desired substance in the blood, provided it is capable of diffusion.  In fact this little apparatus has been found in practice to compare favorably with the kidneys themselves in removing even a lethal dose of poison.”

I watched in amazement.  He was actually cleaning the blood of the dog and putting it back again, purified, into the little body.  Far from being cruel, as perhaps it might seem, it was in reality probably the only method by which the animal could be saved, and at the same time it was giving us a clue as to some elusive, subtle substance used in the case.

“Indeed,” Kennedy went on reflectively, “this process can be kept up for several hours without injury to the dog, though I do not think that will be necessary to relieve the unwonted strain that has been put upon his natural organs.  Finally, at the close of the operation, serious loss of blood is overcome by driving back the greater part of it into his body, closing up the artery and vein, and taking good care of the animal so that he will make a quick recovery.”

For a long time I watched the fascinating process of seeing the life blood coursing through the porous tubes in the salt solution, while Kennedy gave his undivided attention to the success of the delicate experiment.  It was late when I left him, still at work over Buster, and went up to our apartment to turn in, convinced that nothing more would happen that night.