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 principal difficulty in judging of the effects of mercury in meningitis, and of the relative value of recorded cases, lies in the uncertainty of diagnosis. Cases of cerebral congestion, in children especially, present at first symptoms very similar to those of simple meningitis, such as pain in the head, vomiting, injection of the eyes, excitement followed by semi-coma, pyrexia, and even convulsion. Many years ago I usually treated such cases with minute doses of perchloride or iodide of mercury, and, as I thought, with moderately good results, but further experience has not satisfied me on this point. Many surgeons prescribe it in traumatic cases, and believe it relieves the fulness of the cerebral vessels, and although Dr. Ramskill ("Reynolds' System"), Stromeyer, and some other authorities might be quoted as still commending mercurial influence in meningitis, the general tendency of modern opinion is decidedly against its value. In many recent text-books, in Dr. Bristowe's for instance, it is not even mentioned. When the malady follows on febrile or eruptive diseases, or spreads from caries - e.g., in the ear-bones - mercury is not likely to relieve it, and in other idiopathic or at least non-tubercular cases, I think aconite, belladonna, and bromides are of more importance in the early stages, and nourishment and perhaps iodides in the later ones. In cases presumed tuberculous I use iodide of potassium, generally with cinchona. Dr. Copeman, when narrating several cases of apoplexy and cerebral disorder in illustration of the beneficial action of mercury, fully adopts the proposition that it cannot prevent inflammation, but may cause absorption of its results - effusions, adhesions, etc.: he strongly advises its use, therefore, in all inflammations of vital organs, after the acute stage is passed (Medico- Chirurgical Review, i., 1872). I have seen it of some service in such cases, but many remain quite unaffected by it.