Page:The Harveian oration, 1873.djvu/27

 and as the quicksilver was poured into the lymphatic injecting-tube to fill these vessels, it frequently ran out in a full stream by the jugular vein, which was opened. This circumstance rendered it evident that the mercury had passed through the whole course of the lacteals and thoracic duct, and had penetrated even into the venous system. It is, I believe, the only instance in which the thoracic duct has been injected from the lacteals on the intestines e

e I have some pleasure in pointing out that by making a reference to the plates of the venerable Professor Arnold, Fasc. i. Tab. i. fig. 2, 1838, it may be seen that the quick-silver injection could sometimes give as correct results as the 'silver method' of modern microscopy for the detection of lymphatics by their epithelium. The figure I refer to shows the fourth ventricle plexus without, the velum interpositum, on the contrary, with, lymphatics injected with piicksilver. The use of the silver method has enabled me to prove that this representation is correct: abundance of choroidal villi can be procured, and very beautiful objects they are when treated with 0.25 per cent, solution of nitrate of silver, from the plexus in the fourth ventricle, but no lymphatic vessels. These can be shown from the velum interpositum by the use of the same reagent. The use of puicksilver as an injection-substance has not always led as happy results as in the instance just given. Not to specify other cases, it is curious to note that the penetra-