Nitrate of mercury ointment appeared first in the Edinburgh Pharmacopœia of 1722. It was made by dissolving mercury in a sufficient quantity of nitric acid, and adding the solution to melted lard gradually. This was not a satisfactory formula, and it was not until 1787 that anything similar was introduced into the P.L., when 1 oz. of mercury, 2 oz. of nitrous acid, and 1 lb. of lard were combined. This was intended, according to Christison, as an imitation of the well-known golden eye salve, which, however, was, as we know it, an ointment of the red oxide of mercury. Other authorities, Paris Dorvault, Gray, etc., have stated that Singleton’s golden eye ointment was an ointment of sulphuret of arsenic, orpiment some say, realgar others. Pliny refers to the use of sandrach (probably realgar) as an application in ophthalmic affections. Apparently the originator of the P.L. nitrate of mercury ointment was a Dr. Thomas Nettleton of Halifax, Yorkshire. In a pamphlet entitled “On a Safe and Efficacious Medicine in Sore Eyes and Eyelids,” by Thomas Dawson, M.D., of Hackney, printed in 1782, the writer relates that he had heard of a yellow ointment specially good for sore eyes, which fifty years previously had been in the possession of Dr. Thomas Nettleton of Halifax, “whose merit as a man and a physician exceeds all encomium.” One day one of Dr. Dawson’s patients told him of a yellow ointment she had had from a Dr. Key, of Manchester, who had been a pupil of Dr. Nettleton’s. Dr. Dawson wrote to Dr. Key, who at once sent him the recipe, which was as follows:-- Take 1 oz. each of aqua fortis and mercury; dissolve and add the solution to 8 oz. of butter melted. To this add 2 drachms of camphor dissolved in 2 oz. of olive oil. About the end of the eighteenth century, a citrine ointment, made with an ounce of mercury dissolved in nitric acid and incorporated with a pound of lard, was introduced into the Hotel Dieu Hospital of Paris, and used to cure itch. The formula was adopted in the Dublin Pharmacopœia, 1807. COLD CREAM. The Unguentum Refrigerans, also called “Ceratum,” appeared in the first P.L., the formula being attributed to Galen. Four ounces of white wax were melted in 1 lb. of rose oil (ol. rosarum omphacinum, that is, olive oil in which rose buds 4 oz. to the lb. had been macerated, the maceration being carried out three times, each time with a fresh lot of roses). The melted oil and wax were to be poured frequently from one vessel to another, stirring in a little cold water meanwhile, until the mixture became white. Lastly, it was to be washed with rose water, and a little rose water and rose vinegar were to be added. DIACHYLON PLASTER.