Admitting then that all the mercurial effects, except those strictly topical, result from its entrance into the circulation, the next inquiry which suggests itself is, in what method precisely it produces these effects.

It is a very common opinion, which seems to rest on incontrovertible evidence, that it affects the character of the blood itself. After the occurrence of sore-mouth, this fluid is stated, when drawn from the body, to present the buffy coat of inflammation. The experiments of Dr. Samuel Wright have determined that its solid constituents are notably diminished, including albumen, fibrin, and red corpuscles; that it abounds in fetid, fatty matter; and that it is more than ordinarily prone to decomposition. The coagulability is impaired, and the coagulum softer than in health. The pallid aspect of those under its influence proves, without the necessity of experiment, the deficiency in red corpuscles. That the mercurial should produce these results by a direct chemical agency, is an idea wholly incompatible with the minuteness of the quantity absorbed. The best explanation seems to be, that it operates upon the vital properties of the red corpuscles and fibrin, lowering their grade of vital energy, and disposing them to fatty degeneration. Hence the excess of fat, at the expense of these ingredients. The offensive odour of the fatty matter is another evidence of the deterioration, which has been undergone in the change. The buffy coat evinces only a relative excess of fibrin over the red corpuscles, not an absolute excess of the former, and cannot be admitted as proof of a sthenic condition of the blood. This depreciation in the character of the circulating fluid is probably one of the agencies, through which mercury exercises its therapeutic influence. it no doubt contributes to the cachectic condition, which characterizes the prolonged and excessive action of the medicine.

But mercury has also a direct influence over the various solid tissues, which it affects according to their several peculiarities of susceptibility. its general action appears to be irritant. The heart is stimulated to increased action. The tissues of the mouth appear to be peculiarly susceptible, and to suffer accordingly. The digestive apparatus feels the disturbing influence, in part perhaps from the direct action of the mercury, but probably still more from sympathy with the inflamed mouth, and the injurious influence of the impaired blood. The various secretory functions are stimulated, in order that they may eliminate the injurious agent. I have already endeavoured to explain why the hepatic function is specially affected. The excessive flow of saliva may be referred in part to the stomatitis. There can, I think, be little doubt that mercury has a special tendency to act on the salivary glands, and that, independently of the sore-mouth, it would promote their secretion in a greater degree than any other except the hepatic; but there is as little doubt that the existence of the stomatitis adds very greatly to its efficiency in this respect, through the well-established physiological law, that a gland is stimulated by any irritation of the tissue near which its secretory duct opens.

But probably the most important alterative influence of mercury is exerted upon the ultimate organic constituents of the tissues, on which it may be supposed to act as upon the living constituents of the blood, hastening their disintegration, and thus revolutionizing in some degree all the working parts of the system, through the removal of the old, and the substitution of new structure. That it has such an operation, is proved by the rapid emaciation which takes place during mercurialization. The effete matters resulting from this disintegration are thrown into the blood, whence they escape by the excretory outlets. Hence in part probably the foreign fetid matter in the blood, and the stimulant influence on the glands whereby it is eliminated. Hence, moreover, the loaded state of the saliva, which, from the analysis given by Simon, contains an increase of solid ingredients over the normal proportion.

In general there is reason to believe that mercury is rapidly eliminated from the system, which seems to be less tolerant of its presence than of most of the other metals. Thus, Orfila states that, in his experiments on animals with different metallic salts, he has found that, after they had been administered for some time, while lead, copper, and silver could be detected in the tissues at the end of six or eight months from the date of their omission, mercury had generally disappeared in eight or ten days, and had been found only in one instance so late as the eighteenth day. {London Med. Times and Gaz., March, 1852, p. 279.)*

* Dr. F. C. Schneider found mercury in the urine invariably in patients under the influence of mercury internally administered, but never when it was applied exclusively by friction to the surface. The elimination of the mercury continues for a considerable time after the suspension of its use. He has constantly found it at the end of a week, in one case at the end of four, and in another at the end chlorides present to effect this object, and ordinarily, therefore, they operate. But, if this should not be the case, they may remain inert until, from some change of diet, or other cause, the materials requisite for the due chemical reaction may become present, and absorption and consequent mercurialization may take place. Whether it is the alkaline chlorides, or some other agent that operates, the result may be the same; and we are thus offered a satisfactory theoretical explanation of a phenomenon, otherwise but very vaguely understood.

But this elimination seems to be not always complete. Reference has already been made to the fact, that mercurialization has come on, in some instances, to all appearance at least, long after any mercury had been taken into the system. it is possible that, in the change of tissue which takes place under its influence while circulating in the blood, there may be matters produced, or set free, capable of forming with the mercury a compound insoluble in that fluid; or chemical re-agencies may be brought into existence which may serve to reduce the metal; in either case, the insoluble mercurial is deposited in the tissue, and must remain until some influence is brought to bear upon it, capable of effecting its re-solution. Hence, possibly, the metallic mercury which is asserted to have been found in the brain and elsewhere. Confirmation of this view is afforded by the observations of Mialhe, Melsens, and others. Thus, Mialhe has shown that, in the presence of an oxygenizing agent, and one of the alkaline chlorides, mercury, in the metallic state, or any of its ordinary insoluble combinations, becomes soluble in the blood; and, according to the experiments of Melsens, iodide of potassium has the similar property of rendering the mercurials soluble. Hence, it is only necessary to suppose that a sufficient excess of one of the alkaline chlorides should, under favourable circumstances for oxidation, be present in the blood, in order to effect a solution of the deposited metal, and thus, detaching it from the tissues, to bring it into the circulation, once more capable of exercising its peculiar influence on the system at large; and it would seem, from the experiments of M. Melsens, that iodide of potassium, given largely, and absorbed freely as it certainly is, ought to produce the same effect. Some observations made by Dr. Wm. Budd afford still further confirmation. in one instance, a patient who had taken mercury largely, but none for five months, was put on the free use of iodide of potassium, and in a few days was profusely salivated, with all the characteristic phenomena of mercurialism. The mercury was probably set free by the iodide of potassium, and thus made capable of acting; and Dr. Budd states that he has seen many other cases of exactly the same kind. (See B. and F. Medico-chir. Rev., Jan. 1853, Am. ed., p. 158.) Some doubt, however, has been thrown upon this property of iodide of potassium, of facilitating the excretion of mercury, by the experiments of Dr. Schneider referred to in a note on the preceding page.

The occasional cumulative action of mercury may be explained on a somewhat similar principle. The metal itself, and its insoluble compounds, can act, after entering the stomach and bowels, only by becoming soluble there. Ordinarily, there is enough of one of the alkaline of six weeks. He did not find the internal use of iodide of potassium to facilitate the excretion of the mercury. (B. and F. Medico-chir. Rev., July, 1862, p. 245.)- Note to the third edition.