454

ELEMENTS OF MATEKIA MEDICA.

to efl'usion, mercurials are sometimes beneficial. On the contrary, whendropsy occurs in old subjects, and when it depends on, or is accompaniedby, general debility, salivation is almost always hurtful. Moreover,when the effusion arises from mechanical causes not removable by mer-cury, as obliteration of any of the venous trunks, or pressure of malignanttumors, salivation is injurious. Occasionally dropsical effusion takesplace without any appreciable cause, and then, of course, if mercury beemployed, it must be in part on speculation. In such cases calomel isnot unfrequently employed in combination with squills or foxglove.

if) In chronic diseases of the viscera, especially those arising from orconnected with inflammation, mercury is frequently serviceable. Thus,in enlargement or induration of the liver, in hepatization of the lungs,&c. In those diseases commonly termed malignant, as cancer and fun-gus hsematodes, and also in diseases of a non-malignant character, butoccurring in debilitated subjects, mercurials, given so as to excite saliva-tion, are objectionable.

iff.) In chronic diseases of the nervous system. —Mercury has beenrecommended in paralysis, and on some occasions has proved exceed-ingly efficacious. I have seen hemiplegia, with impaired vision andhearing, headache, and cramps of the extremities, recover under the useof mercury, after blood-letting, purgatives, &c. had failed. The patient(a young man) was kept under the influence of the medicine for twomonths. Mr. Colies {op. cit. p. 327) has likewise found it most effica-cious in paralysis. In tetanus, mania, epilepsy, hysteria, tic douloureux,and other affections of the nervous system, mercury has been used withoccasional benefit.

The foregoing are some of the more important diseases against whichmercurials have been successfully administered as sialogogues.

Ilydrar'(jyrum cum Cre'ta. — Mer'cury with Chalk.

History. — This compound (called also mercurius alcalisatus, orcethiops absorbens) is first mentioned, I believe, by Burton, in 1738.

Preparation. —It is prepared by rubbing three ounces of mercury withfive ounces of chalk, until globules are no longer visible. On account ofthe tediousness of the process, the friction is usually effected by steam.

If this powder be digested in acetic acid, the lime of the chalk is dis-solved, and the carbonic acid escapes ; but the greater part, if not the wholeof the mercury, is insoluble in the acid, and hence is not the protoxide.If examined by a lens, the residuum is found to consist of minuteseparate globules, which readily whiten silver and gold, showing they arein the metallic state. Hence it is probable that the quicksilver is, forthe most part, mechanically divided only, but a small portion may per-haps be oxidized.

Properties and Characteristics. —It is a greyish powder, whicheffervesces on the addition of acetic acid, yielding a solution of lime,which may be distinguished by the tests for the calcareous salts alreadymentioned. By digestion in nitric acid, we obtain a solution known tocontain mercury by the characters already detailed for the mercurialpreparations generally. By heat the mercury is volatilized, leaving thechalk.

Composition.— It consists of mercury and chalk, with perhaps a little