Page:Proceedings of the Royal Society of London Vol 1.djvu/415

Rh conveyed; but brings forward the present set of experiments to correct that opinion, which he ﬁnds to be erroneous.

Mr. Brodie having tied the thoracic duct in some experiments of his own, it occurred to Mr. Home, that under these circumstances the existence or non-existence of any other channel from the stomach into the circulation might be fully established.

A rabbit and a dog were each subjected to this experiment. After tying the thoracic duct, 9. quantity of infusion of rhubarb was inject- ed into the stomach; and, in an hour after, the urine was examined, and found to be tinged with the rhubarb. In the dog, the bile was also examined, and found to be tinged with the rhubarb. The existence of a channel distinct from the thoracic duct being thus established, the experiment was repeated on a dog whose spleen had been removed four days previously; but still the urine became tinged with the rhubarb, so that the channel is not through the spleen.

As it was possible (though not very probable) that the rhubarb might, by some unastomosis, obtain a passage through the lymphatic vessel, which enters at the angle between the jugular and subclavian veins on the right side, the same experiment was repeated upon an— other dog, in whom this vessel was also secured by ligature, us well as the thoracic duct, previously to the injection of the rhubarb; but in this experiment also the rhubarb found its way to the bladder, as before. When the spleen of this dog was infused in water, the in- fusion was slightly tinged with the rhubarb; but when the liver was - infused, the proportion of blood present was so great as not to admit of determining whether rhubarb was present or not.

In some of these experiments the thoracic duct was wounded or ruptured, so that cher was found to have ﬂowed from it, and was collected for experiment: in other experiments the duct itself, the mesenteric glands, and lacteals, were found distended, and the ﬂuid was pressed from them for the same purpose; but it was in no instance found to be tinged with the rhubarb.

These experiments, says Mr. Home, completely establish the fact, that the rhubarb did not pass through the thoracic duct, and also completely overturn the opinion of the spleen being the medium by which it was conveyed. He conceives, therefore, that the rhubarb found in the spleen must previously have entered the circulation, and thence have been deposited, by secretion, in the cells of the spleen. The objection to this opinion is, that there is no excretory duct from the spleen; but Mr. Home observes, that the lymphatic vessels probably perform the ofﬁce of excretory ducts, as they are both larger and more numerous than in any other organ of the body. In the ass, he remarks, they unite and form one common trunk; and as they terminate in the thoracic duct, it would be a deviation from the general plan of the animal economy if their structure differed from that of other lymphatic vessels.