salivation Dr. Davidson of Glasgow has lately proposed a character, the exact scope of which cannot yet be appreciated,—namely, that in true mercurial salivation there is never any sulphocyanic acid in the saliva; so that sesquichloride of iron does not render it red. The presence of sulphocyanic acid may possibly prove that salivation is not mercurial; but the converse does not hold good, because other causes tend to deprive human saliva of its sulphocyanic acid.[1]
The next point to be noticed regarding mercurial salivation is, that a long interval may elapse after the administration of the mercury has been abandoned, before the effect on the salivary glands and mouth begins,—mercury in small doses being what is called a cumulative poison, or a poison whose influence accumulates silently for some time in the body before its symptoms break forth. Swédiaur has met with instances where the interval was several months,[2] Cullerier with a case in which it was three months.[3] It will at once be seen how strongly such facts may bear on the evidence in a criminal case, where the administration of mercury in medicinal doses, which have been long abandoned, is brought forward to account for salivation, appearing weeks or months after, and giving rise, in conjunction with other circumstances, to a suspicion of mercurial poisoning of more recent date.
Another question which has been made the subject of discussion is the duration of mercurial ptyalism. The medical witness may be required to give his opinion how long this affection may last after the administration of mercury has been abandoned. The present question may be cut short by stating, that there appears to be hardly any limit to its possible duration. Linnæus met with an instance of its continuing inveterately for a whole year;[4] Swédiaur says he has known persons languish for months and years from its effects;[5] and M. Colson knew an individual who had been salivated for six years.[6] These, however, are very rare incidents. After an ordinary mercurial course the mouth and salivary glands generally return to the healthy state in the course of a fortnight or three weeks.
A fifth question, whether the ptyalism, or, speaking in general terms, the erethysm of mercury, is susceptible of a complete intermission, formed a material subject of inquiry, and the cause of much contradictory statement on a noted criminal trial, that of Miss Butterfield in 1775 for the murder of her master, Mr. Scawen. She was accused of administering corrosive sublimate; and it was alleged in her defence, that the salivation and consequent sloughing of which he died might have arisen, without the fresh administration of mercury, from the renewal of a previous ptyalism, which had been brought on by a common mercurial course, and had ceased two months before the second salivation began. It appeared that Mr. Scawen was salivated with a quack medicine from the beginning till
