“The rectified spirit of urine[424] could be substituted for the human urine. One should then take two drams of this substance and mix it with two or three ounces of aqua vitæ, or water of cresses or of cochlearia. Sal volatile[425] has the same virtues. Those who wish to make use of it should dissolve fifteen to thirty grains of it in the same quantity of the above liquid.” Fauchard then passes on to speak of trepanning of the teeth when they are worn away or decayed and cause pain.[426] He begins by saying that most varieties of pain caused by the canines and the incisors when worn away or decayed cease after the use of the trepan. He, however, understands the term trepanning in a very wide sense, comprehending therein the use of any instrument whatever (even a needle or a pin) with which one penetrates into the inner cavity of the teeth. In interstitial caries of the canines and incisors one ought, says Fauchard, first to enlarge the interstice with a small file of a convenient shape, then to scrape the decayed cavity, and finally to open up the canal or inner cavity of the tooth with a perforator or with a small trepan. “In this way the pus or other humors that may have collected in the tooth can easily find their way out, and the pain will cease at once or in a short time.” The author describes with much minuteness the manner of trepanning, and then adds: “After this operation one should let a few weeks pass without doing anything to the affected tooth, and afterward, in order to impede further decay, one must put a little cotton-wool into it soaked in oil of cinnamon or of cloves. The tooth must be left in this state for some months, taking care to renew the cotton-wool. It is necessary to observe that in beginning to put in the cotton-wool this should be done with lightness and without pressing it down much, so that if pus should gather again it may be able to make its way through the cotton-wool, the principal object of this being to hinder the penetrating of alimentary substances into the tooth, which would be the cause of further decay. If the cotton were pressed into the tooth from the beginning, the pus, not being able to find an exit, would accumulate, and might cause much pain, if the nervous parts of the tooth were not yet dried up or destroyed. The same thing might happen after the application of a lead stopping, and one would be obliged to remove it and let considerable time pass before putting it in again.”