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 applied externally have caused violent ptyalism and death in eight days. On the other hand, it is well known that some constitutions resist the action of mercurials very obstinately, so as even sometimes to appear incapable of being salivated at all. I have more than once met with cases of the last description, where mercurial courses had been continued for three months and upwards without avail. It may be added, that, except in constitutions naturally predisposed to suffer from a few small doses, a few large doses do not appear apt to excite severe salivation, or even to cause any at all. This has been clearly shown in the course of the practice lately introduced of administering calomel in doses of a scruple. On that subject more will be said by and by. At present I may mention, that, in conformity with the practice alluded to, I have several times, in various diseases, given eight or ten grains of calomel five or six times a day for two or three days together, without observing that ptyalism was apt to ensue.

The next point to be considered is, whether mercurial salivation can be confounded with any other affection. In a very difficult case of poisoning which was tried here in 1817, that of William Patterson for murdering his wife, it appeared probable that he had given her repeatedly large doses of calomel. But the proof of this was circumstantial only, and an important circumstance in the chain of evidence was a deposition to the occurrence of salivation during the woman's illness. This fact, however, rested on the skill and testimony of a quack-doctor only; and the admissibility of such a person to decide on a point of this nature, will depend on the facility with which the true mercurial form of salivation can be recognised. This statement will show the practical object of what is to follow.

Many other causes may excite a preternatural flow of saliva. Several other poisons may have that effect, for example, preparations of gold, preparations of copper, antimony, croton-oil, and foxglove: foxglove has been known to cause violent salivation for three weeks. Opium too has occasionally excited salivation, and also hydrocyanic acid and iodide of potassium.

Even a common sore throat, if the swelling and pain are so great as to render swallowing very difficult and distressing, may be accompanied, as every physician must have remarked, with a profuse flow of saliva; and in the ulcerative stage there is also often a fetor that is hardly distinguishable from the mercurial kind. In the ulceration of the mouth called cancrum oris there is some salivation with great fetor of the breath.

Salivation likewise forms an idiopathic disease, and may then be both profuse and obstinate. Mr. Davies has described a case of spontaneous ptyalism which had lasted for a fortnight before he was called to see the patient; and during all that time the quantity of saliva discharged was two or three pints daily. How long it endured afterwards he does not mention; but it must have continued for some time, because during his attendance first one physician and