Physiological Action (External)

The local action of mercury varies according as to whether the metal itself is used, or one of its soluble or insoluble compounds, and of course according to the strength of the preparation; and on account of the volatility and the ready absorption of the drug, its local use often induces its systemic effects.

Metallic mercury produces upon the skin no other local effect than a sense of coldness. Mercurial ointment applied by friction is usually well borne, but sometimes excites a red or vesicular eruption (mercurial eczema), more or less intense; ointment of the red oxide is painful to sensitive parts, and that of the red iodide may irritate very severely, even to vesication: if not perfectly fresh an additional source of irritation is found in rancid lard: good calomel ointment is rather soothing than otherwise.

A strength of 2 gr. of corrosive sublimate in the ounce of liquid suffices to destroy parasitic life; a stronger lotion irritates. Cloquet, the distinguished anatomist, suffered from severe local and general symptoms after handling some preparations steeped in a strong solution. A proportion of 10 gr. to the drachm of alcohol vesicates, and when applied to the scalp has caused death in a child (Lancet, ii., 1871). In two other children, the use to the scalp of an ointment containing 120 gr. to the ounce of tallow also caused death (Dublin Journal, August, 1854). The solution of the metal in nitric acid (liquor hydrargyri nitratis acidus) is a powerful and painful caustic, and its application has sometimes, though not frequently, been followed by severe general symptoms: it combines with albumen and fibrine, producing a white eschar.

On the mucous membrane of the intestinal tract mercurial compound's may exert a local action of the same nature as upon the skin. Quicksilver, in doses of 1/2 oz. or more, will usually pass through the intestine by its mechanical weight, and unaltered; sometimes it has caused perforation.

Physiological Action (Internal)

In studying the action of this medicine, it is more than usually important to distinguish between the effects of small and of large doses. Modern observation shows us that the former are rather of tonic and constructive character, while older records have told us only too well the fatally destructive results of the "heroic" administration of the drug. I do not mean simply that one grain, e.g., of calomel has a different effect from twenty: we must estimate the dose rather by what is absorbed of it, and by the results shown, especially by the state of the mouth and the secretions. Practically we can either give the medicine so as to cure without marked effect upon these, or so as to produce only moderate effects, and it is this "slight mercurialization" which requires to be distinguished from the severe form which should be called rather mercurial poisoning, and is accompanied with stomatitis, salivation, diarrhoea, cachexia, etc. A similar difference of degree exists, of course, in the action of all powerful medicines, but it requires more attention in the present instance, because our predecessors thought to give benefit only by what we consider a poisonous action of the drug, and it consequently fell into undeserved discredit. There is, further, a chronic form of mercurial poisoning which may still be met with in various trades, and this differs in some respects from any condition produced by modern medication.

Circulatory System

Recent observations as to the action of mercury on the blood illustrate well its different effects, since they show that, in quite small doses, it increases the number of red corpuscles, and improves the blood-condition. Grassi proved this by analyses, and Wilbouchewitz counted carefully under the microscope the average number contained in a millimetre-cube, and his patients (ten in number) then took either 2/3 gr. of sublimate daily, or 1/6 gr. of proto-iodide: during the first fortnight of treatment the increase of corpuscles amounted to nearly one million.

These patients were syphilitic, and probably the anaemia of their malady was benefited by the antidotal action of the mercury, for the remedy being continued beyond a certain time (and thus allowed to accumulate in the blood), the red globules diminished in number, so that, by the end of the second fortnight, they counted the same as before any treatment. Mercury being then omitted altogether, the corpuscles increased again within a week's time. The inference is clear - too much of the drug im-paired the blood-condition, but a little improved it. When it was omitted, and when, after a few days' time, only a small proportion remained in the blood, the original improvement was again observed: the white globules varied in an inverse ratio (Archives de Physiologie, 1874). Keyes repeated these observations, and concluded that small doses of mercury increase the blood-corpuscles in all subjects, whether syphilitic or not; and further, that this increase is not temporary: he has never seen hypoglobulism- i.e., a lessened average number of corpuscles, caused by small doses (American Journal, January, 187G). Possibly the difference between these two observers may arise from difference in dosage, Wilbouchewitz giving the rather large quantity of "2/3 gr. sublimate daily;" no doubt mercury in any form, continued long enough, and absorbed, will produce a destructive effect on the corpuscles, and a condition of "spanaemia." Long ago, Bretonneau and Dumont reported that the blood-clot in mercurialized animals was either absent or was soft and diffluent. Headland's expression is that mercury "disintegrates and decomposes the blood" (Lancet, i., 1858), and Wright's analysis showed it to be more fluid and less coagulable than normal, its albumen, fibrine, and red globules being diminished, and a foetid, fatty material being formed in it. Gubler has also corroborated this destructive effect, and yet Lemaire and Gelis found "mercurial treatment to increase plasticity of blood." Autenrieth questions the analysis of Wright, and more lately Overbeck found in animals poisoned by mercury the venous blood dark and thick, the arterial blood clear and coagulating well, fibrine increased: probably these results were connected with inflammatory reactions, but, if verified, they tell much against any available "aplastic power" of mercury in inflammation; still, the ultimate effect of the drug is destructive. Polotebnow, adding mercurial albuminate to the blood of dogs, found the corpuscles rapidly destroyed, with loss of haematine and pigment (Schmidt's Jahrb., 18G5, 125, 3). Wilbouchewitz, giving calomel to rabbits (and not in large doses), noted a rapid diminution of corpuscles. Trousseau found that leech-bites that had ceased bleeding, bled again in patients submitted to mercurial treatment, but beyond any single fact is the general experience that too much of the drug induces - after a period of malaise, restlessness, and febrile symptoms - a chlorotic pallor of the skin, with signs of enfeebled circulation, distress in breathing, intermittent pulse, and palpitation; such a condition, when fully developed, is difficult of cure; it may last long, and end fatally.

Fothergill includes mercury among his "cardiac depressants," and G. Harley, having injected sublimate into the femoral vein of a dog, found that cardiac paralysis was produced before intestinal contractions ceased ("Proceedings of the Royal Society," 1864).