He warns those who suffer from odontalgia not to have recourse thoughtlessly to tooth-drawers, but to recur, instead, to the doctor, who will always treat the affection according to the cause on which it depends. And here the author repeats the numerous distinctions found in many preceding writers, and especially in Arculanus. The pain may be located in the gums, in the dental nerve, or in the very substance of the tooth; and in each of these cases it may depend on warm or cold matter, on dryness, humidity, etc. [Illustration: FIG. 76 A Dutch dentist. (From a picture of the XVI century.) By Lucas Van Leyden.] The method of treatment must vary in all these cases; and in regard to this the author enters into minute particulars, commencing with dietetic cure—which itself must be varied according to the causes of the affection—and then treats of all the other therapeutic means—purgatives, bloodletting, revulsives, local narcotic or resolvent medicaments, and so forth. The letting of blood was, it seems, a very favorite method of cure; not only were the veins of the arm opened, but also those of the tongue, of the gums, of the lips, and of the ears! Another remedy which the author seems to have a predilection for is oil of vitriol. When a tooth shows a carious perforation, he applies inside it, by means of a split feather, a drop of oil of vitriol, which, says he, causes the fall of the tooth after a few days. Elsewhere he says that “sometimes worms are produced in carious teeth; to kill them a drop of oil of vitriol is an excellent remedy; and this at the same time cures the decay of the tooth and takes away the sensibility of the nerve.” This passage does not agree very well with the preceding one, according to which oil of vitriol would act much more radically by causing the tooth to fall out altogether. But we will not take exception to so small a matter; so much the more, as the author, if he were still alive, might perhaps show us by some subtle distinction that the contradiction alluded to is only an apparent one! To free the teeth from tartar, Heurn likewise counsels oil of vitriol, diluted, however, with other liquids. A tooth must not be sacrificed excepting when it is loose and attacked by incipient necrosis, so as to leave no hope of arresting the putrefactive process. It is then our duty, says Heurn, to remove the tooth without causing much pain. For this purpose, after the tooth has been separated all around from the gums, it must be raised somewhat from the alveolus; then it must be sprinkled with powder of euphorbia, or a paste made with flour and the juice of the tithymalus must be applied around it, taking care, however, to cover the neighboring teeth with wax. After two or three days the tooth will be so loose that it can be pulled out very easily with the fingers or with a pair of pincers.