About five minutes after a few drops of a solution of hydrochloride of Cocaine composed of 0.5 gramme of that salt to a gramme of distilled water have been instilled into the eye, anæsthesia of the conjunctival mucous membrane of the cornea begins to manifest itself and reaches the deep parts in about fifteen or twenty minutes if the instillations are repeated every five minutes.
At the same time there is a certain amount of mydriasis, but this is less pronounced than that produced by atropine. This pupillary dilatation, which is more perceptible in young subjects and not in glaucomatous states, lasts, at least, for twenty-four hours. With that occurs a slight paralysis of the ciliary muscle.
"On account of this," says Professor Panas, "Cocaine should be placed among the slightly mydriatic substances of which the passing effect might be utilized for ophthalmoscopic explorations of the fundus of the eye, under the same head as, and better than, homatropine."
According to M. Dujardin-Beaumetz, Cocaine not only deadens sensibility, but it can further be utilized with morphinomaniacs as a substitute for morphine without presenting the objections of the latter substance; and he adds that subcutaneous injections made with this alkaloid are not irritating (Bulletin de l'Académie de Médecine, session of the 18th of November, 1884).
Prof. Vulpian, at the outset, communicated to the Académie des Sciences the results of his interesting physiological researches with the chlorhydrate of Cocaine.
M. Vulpian, after observing similar anæsthetic and analgesic effects on the eye in animals as already shown in man, resulting from an instillation between the eyelids of a few drops of solution of hydrochlorate of Cocaine, and also perceiving under these conditions the mydriatic action of the salt, noticed a protrusion of the ocular globe when he injected 0.10 centigramme of hydrochloride of Cocaine of a one to one hundred aqueous solution into the saphenous vein of a non-curarized dog, and that it occurred almost immediately after throwing the liquid into the vessel. Instantly the eyelids were seen to separate and the pupillary orifice to enlarge. "This," says he, "is an effect which exactly recalls the results of faradization of the upper extremity of the cervical sympathetic nerve cut transversely."
Complete anæsthesia of the two transparent corneæ existed in this case.
Prof. Grasset, of Montpelier, almost at the same time as Vulpian, observed the same effects of Cocaine, but a greater persistency in the phenomena of insensibility following the intravenous injection of the solution of hydrochloride of Cocaine.
At about that time, Dr. Laborde, of the Académie de Médecine, treated still more deeply of the action of Cocaine in three successive notes to the Société de Biologie (Nov. 22d and 29th and Dec. 27th, 1884). This learned physiologist studied the analgesic action generally resulting from subcutaneous injections of 0.03 of hydrochloride of Cocaine, in three doses, in the guinea-pig. He saw it at the same time produce a general hyper-excitability which irresistibly forced the animal to move, and even produced epileptic convulsions; the general analgesic state lasted for more than forty-eight hours.