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.
Stille, after giving many authorities in favor of the mercurial treatment of diphtheritic disease, says himself "that it appears urgent that the system should be brought under mercurial influence as speedily as possible," and following Albers, he recommends 1/4 gr. of calomel every hour, and a scruple of mercurial ointment to be rubbed at intervals into the thighs. Trousseau, finding that the direct application of calomel to external diphtheritic surfaces modified favorably their condition, recommended its use by insufflation, or by allowing it to mingle slowly with the saliva; this has not, however, given much result. Bretonneau used mercurials freely, but his mortality was great, and contributed to induce a general distrust of the treatment. West, however (Ed. 1859), still considered calomel useful for "counteracting the tendency to formation of false membrane and preventing lung-inflammation." I have been myself much disappointed with the action of calomel in these respects, but the red iodide and the cyanide of mercury, in doses of 1/50 to 1/30 gr. every two to four hours, have exerted a more favorable influence in some severe cases. It is very important to watch their action carefully, and not to induce salivation, for according to general experience "this promotes rather than checks the spread of exudation" (Mackenzie), and certainly, as a general rule, other remedies of a tonic or antiseptic character are often to be preferred to mercurials.