No direct effect on the blood can be attributed to mercury; but impairment of nutrition generally, including digestion, attends its excessive use, and induces impoverishment, both of the plasma and the corpuscles, indirectly referable to the drug. The blood under these circumstances is more watery and coagulates less firmly, and nutrition may be further disordered in consequence, with the production of low forms of inflammation and ulceration. But it is to be clearly understood that this is not in any sense a specific effect of mercury, and that the in-fluence of mercury upon inflammatory products and syphilitic growths, to he presently described, is not exerted through the blood, but upon the tissues themselves. The impoverishing effect of this drug upon the blood must be constantly kept in mind, and the quality of the blood sustained by abundance of food, and the strictest attention to digestion.

3. Specific Action

Mercury quickly leaves the blood and enters the tissues, where it is apt to remain almost indefinitely, being excreted with comparative slowness, especially when the kidneys are diseased.It has been found in every organ of the body, most abundantly in the liver. It is a remarkable fact, however, that no definite anatomical change has ever been demonstrated in the viscera, such as the vessels, liver, or nervous system, even in cases of chronic poisoning by this metal; mercury in this respect again differing from lead, silver, antimony, and arsenic. whilst, therefore, the specific action of mercury is unquestionable, its mode of action is still obscure, and numerous theories have been proposed to account for it, which need not be fully discussed here. The most probable explana-tion of the effects of mercury upon nutrition may be said to be that in some way or other it interferes with the growth or life of germinal cells, and that it has therefore an alterative in-fluence on certain processes, such as inflammation and syphilis, which are characterised by a growth of small young cells. Possibly, it may have a destructive influence on certain ferments and organisms connected with physiological and pathological metabolism, one of these being the organism of syphilis.

Whatever may be the explanation of its action, mercury produces a train of symptoms, when given for a considerable period in moderate doses, known as "hydrargyrism," which chiefly take the form of debility; nervous phenomena, including muscular tremors and paralysis, pains, and mental disturbance; cardiac depression; ulceration of the skin, mouth and mucous membranes; salivation, dyespepsia. and diarrhoea. The temperature is not directly raised, nor the exerectiontions increased, so that there is no positive evidence of increased metabolism as an effect of mercury.

4. Specific Uses

The uses of mercury as a specific remedy bear no definite relation to these effects, which have been mentioned chiefly that they may be recognised and arrested. The principal application of the drug is as an "alterative" in syphilis, a disease attended by the growth of cells around the small vessels, and the development of these into nodes, gummata, various eruptions, etc. Mercury has a powerful influence in controlling the severity of this disease. Its employment may be commenced with various local applications to the primary sore, and regular internal doses of the solution of the per-chloride, calomel, grey powder, or some of the other preparations, until salivation threatens. It is generally (not universally) believed that the secondary stage is rendered less severe, or is even entirely prevented by this means. The drug must be continued during the appearance of secondary symptoms; but, as a rule, it is better omitted in the tertiary stage. The particular preparation employed varies with the experience of the practitioner. Quinine and opium are useful means of support to be combined with mercury in a course of the metal, and we must repeat that, unless the appetite and digestion continue good, its use must be interrupted.

The other use of mercurials as alterative remedies is in internal inflammations, especially inflammation of serous membranes, such as peritonitis, pericarditis, pleurisy, meningitis, and orchitis. This line of treatment, once universal in England, is now almost obsolete, excepting, perhaps, in peritonitis of a subacute or chronic kind, in which, as in most instances where it is used as an antiphlogistic, mercury is combined with opium. Possibly some of the benefit thus attending mercurialisation in inflammation, and which was formerly referred to a "resolvent" action on the fibrin of exudations, is due to its purgative and indirect cholagogue effects.

5. Remote Local Action And Uses

Mercury passes out of the system in all the secretions - the saliva, sweat, milk, urine, and bile, probably as an albuminate, and stimulates many of the glands en route. It is in this way, as we have seen, a powerful sialagogue, causing swelling of the salivary glands and a profuse flow of the secretions of the mouth. This effect is important only because it is to be avoided. The diaphoretic effect of mercury is comparatively insignificant. Whilst it does not increase of itself the volume !of urine, it assists to a marked degree such diuretics as digitalis and scilla; but it must not be given in kidney disease, as it acts injuriously on the diseased tubules, and readily produces its debilitating effects when the renal function is impaired. In the faeces mercury leaves the body as the sulphide, being derived, first, from that considerable portion of the dose which is not absorbed; and, secondly, from the portion excreted by the liver (in the bile), and by the pancreas and intestinal glands. It will thus be seen that but little use is made of the remote local action of mercury.

6. Action And Uses Of The Different Preparations Of Mercury

The preparations of mercury, although so numerous, can be readily remembered, and their special actions understood, when they are classified as follows: