This is peculiar to the U. S. Pharmacopoeia, having been introduced into it as a substitute for the vinegar of opium or black drop. It is made by macerating opium in a mixture of vinegar and alcohol. The only advantage that is claimed for it over laudanum is that it is somewhat weaker in alcohol, and that the active principles of the opium arc modified by the acetic acid of the vinegar. The only known method in which such a modification could be produced, is that the acetic acid may take the place of the meconic acid, and form an acetate instead of meco-nate of morphia and the other alkaloids of opium. But, whatever may be the theory in the case, the preparation appears to agree with certain patients, who cannot take laudanum conveniently, in consequence of the headache, delirium, nausea, or other nervous disorder which it produces. It was a favourite with the late Dr. Joseph Hartshorne, of Philadelphia, who introduced it into notice, and whose large experience entitles his recommendation to great weight. The dose of it, equivalent to a grain of opium, is ten minims, or about twenty drops.