This section is from the book "Materia Medica And Therapeutics Inorganic Substances", by Charles D. F. Phillips. Also available from Amazon: Materia medica and therapeutics.
The question whether mercury can be absorbed in its metallic state, either by the skin or the digestive tract, has scarcely yet passed from the region of debate, and contradictory facts have been alleged concerning it. Von Hasselt found the metal in the blood of mercurialized persons (Stille), and Colson obtained a deposit of it from a brass plate placed for a time in contact with blood drawn from a patient who had taken the drug (Archives Gen., xii., p. 86). Claude Bernard filled the medullary cavity of a dog's femur with quicksilver, closed the perforation with wax, and allowed the soft parts to heal; three months afterward most of the metal had disappeared from the bone, and was found in small globules encysted on the surface of the lungs. In another dog the metal was injected into the jugular vein, and twenty-five days afterward found "divise a, l'infini," in the cardiac tissue under the pericardium, so that it would not remain in the blood, though taken up by it. Oesterlen used mercurial frictions on cats, giving them also internally pills of blue ointment, and he reported the finding of mercurial globules, not only in the skin, but in most of the organs. Overbeck confirmed these results on rabbits (quoted by Stille), and Blomberg detected mercurial corpuscles in cats to which he had given pills of citrine ointment ("Treatise on Absorption of Mercury," Hel-singfors, 1868). The latter observer used mercurial friction on the arm of a dead body, and found globules in the corium and mucous layers, but not deeper.
Such observations would seem conclusive, but that Barensprung, Rindfleisch, and others find it impossible to verify them: they have made the frictions and given the pills, but they cannot find the metal in the blood, nor yet in the corium. Autenrieth could find no amalgam on plates of gold introduced into the subcutaneous tissue under the place of friction, and Gubler and Neumann, while they recognized the metal in the sweat-glands and hair-follicles, could trace it no further. Rindfleisch, it is true, found mercury once in mesenteric glands after giving mercurial pills, but there were ulcerations in the intestinal mucous coat which might have permitted the passage of the metallic globules (Archiv fur Dermatol., iii., 1870). The most recent observations are those of Fleischer, who concludes from numerous experiments, that "frictions with mercurial ointment cause the penetration of metallic particles into the superficial layers of epidermis, but not deeper:" and a consideration of the whole evidence warrants this negative conclusion, that although metallic mercury, when administered by the mouth in substance, or actually placed within the tissues, may circulate and be deposited, it does not seem to be altered or absorbed in the ordinary sense, and when applied by friction it usually does not pass either into the deeper tissues or into the blood.
The physiological effects of mercurial frictions must be connected, therefore, with its absorption in some other form: either mercurial vapor is inhaled during the process, or a sebacic oxide of mercury enters through the skin. As to the former point, we know that sometimes salivation has occurred in a wife, six hours after a friction made by the husband upon himself only, both living in rather a small room (Samelsohn, quoted by Hallopeau); and additional evidence in favor of such an effect is furnished by the delicate observations of Merget. He demonstrated that mercury volatilized at all temperatures, and, by means of iridium-paper (which showed a dark stain on contact with the vapor), he proved its presence on the hands or other parts of the body of persons who had spent only a few hours in a workshop where it had been used (Comptes Rendus, December, 1871). That the mercurial vapor is not absorbed only by the lungs is evident from a carefully devised experiment by Fleischer (Er-langen): he caused frictions to be made upon an arm while the patient- with face covered by a mask - breathed only external air; the limb was then carefully wrapped in wool and oiled silk for sixty hours, and during that time the presence of mercury (in very small quantity) was verified in the urine.
We may state then that mercurial vapor is absorbed, not only by the lungs but also by the skin, and indeed the results of ordinary fumigations - when the head is external to the apparatus - would be sufficient to prove this. Gubler holds that the sweat-glands are the active agents in this absorption, and Rohrig admits that mercury in vapor can pass through the epidermis (Strieker's Jahrb., ii. 1873). It is probable also that some may be absorbed as oxide in combination with fatty acids (sebacic), or acids contained in the perspiration (Christison). Baren-sprung and others have proved the presence of such oxide in "blue ointment;" Nevins calculated it at 1 part in 100, and Voit, analyzing portions of skin which had been rubbed with it, found the oxide constantly present. A soluble double salt may be formed with the chlorides of the perspiration (Muller), and, if mercurial oxides be given internally, Voit argues that the chlorides of the blood can change suboxide into calomel and peroxide into perchloride, which salts then combine with sodium chloride and albumen.
Metallic mercury, given by the mouth, usually passes off unchanged by the bowel; in the rare cases where it has given rise to constitutional effects, a portion has probably been oxidized or changed into sublimate. In the very finely divided form, when the metal is "extinguished" by continued friction with chalk (gray powder), or with confection of roses (blue pill), Rabuteau thinks it may be directly absorbed from the intestine, but no doubt some oxidation occurs during trituration, and the oxide would be soluble more readily in the acid of the gastric juice; mercury in a volatile form would also be disengaged from such compounds as readily within the body as without, at the same temperature. Mercurial ointment or pill, introduced as a suppository into the rectum, produces physiological effects perhaps more quickly than by the stomach. In the various trades which require the handling of quicksilver - such as barometer- and mirror-making, gilding, and skin-dressing, and again, in miners at Almaden and elsewhere - the physiological effects produced are mainly traceable to inhalation of the vapor.