§ 10. Proust[23] observed that a very fœtid hydrogen gas was disengaged when arsenical tin was dissolved in hydrochloric acid, and that arsenic was deposited from the inflamed gas on cold surfaces which the flame touched. Trommsdorff next announced, in 1803, that when arsenical zinc was introduced into an ordinary flask with water and sulphuric acid, an arsenical hydrogen was disengaged; and if the tube was sufficiently long, arsenic was deposited on its walls.[24] Stromeyer, Gay-Lussac, Thénard, Gehlen, and Davy later studied this gas, and Serullas in 1821 proposed this reaction as a toxicological test. Lastly, in 1836, Marsh published his Memoir.[25] He elaborated a special apparatus of great simplicity, developed hydrogen by means of zinc and sulphuric acid, inflamed the issuing gas, and obtained any arsenic present as a metal, which could be afterwards converted into arsenious acid, &c.
[23] Proust, Annales de Chimie, t. xxviii., 1798.
[24] Nicholson’s Journal, vol. vi.
[25] “Description of a New Process of Separating Small Quantities of Arsenic from Substances with which it is mixed.” Ed. New. Phil. Journal, 1836.
This brief history of the so-called “Marsh’s Test” amply shows that Marsh was not the discoverer of the test. Like many other useful processes, it seems to have been evolved by a combination of many minds. It may, however, be truly said that Marsh was the first who perfected the test and brought it prominently forward.
§ 11. Matthieu Joseph Bonaventura Orfila must be considered the father of modern toxicology. His great work, Traité de Toxicologie, was first published in 1814, and went through many editions. Orfila’s chief merit was the discovery that poisons were absorbed and accumulated in certain tissues—a discovery which bore immediate fruit, and greatly extended the means of seeking poisons. Before the time of Orfila, a chemist not finding anything in the stomach would not have troubled to examine the liver, the kidney, the brain, or the blood. The immense number of experiments which Orfila undertook is simply marvellous. Some are of little value, and teach nothing accurately as to the action of poisons—as, for example, many of those in which he tied the gullet in order to prevent vomiting, for such are experiments under entirely unnatural conditions; but there are still a large number which form the very basis of our pathological knowledge.
Orfila’s method of experiment was usually to take weighed or measured quantities of poison, to administer them to animals, and then after death—first carefully noting the changes in the tissues and organs—to attempt to recover by chemical means the poison administered. In this way he detected and recovered nearly all the organic and inorganic poisons then known; and most of his processes are, with modifications and improvements, in use at the present time.[26]