This is necessary, as the surgeon must introduce his finger into the mouth and behind the cheek to mold out the mass injected subcutaneously, and infection could easily be introduced by his fingers during this procedure. Externally a generous field of the operation is scrubbed with a brush dipped into green soap and water. The skin is then thoroughly washed with gauze sponges steeped in absolute alcohol, followed with spongings with a 1-5,000 solution of bichlorid of mercury. The whole surface is then wiped off with a sponge dipped in ether and covered for the time being with a pad of sterilized gauze until the operator is ready to proceed with the operation. PREPARATION OF THE INSTRUMENTS FOR OPERATION The manner of preparing the necessary mixture of paraffin has been described on page 244. After such preparation, the mixture, still hot, may be poured into test tubes, which are sealed and put away for further use, each tube holding just enough to fill the syringe two thirds full. When a syringe is to be filled, one of the tubes is opened and the contents are again boiled over a spirit flame, or simply liquefied and poured into one of the types of heaters already described for the same purpose of resterilization. From the test tubes or the heater, the boiling mixture may be drawn up into the sterilized syringe to the required amount or it may be poured into the opened piston screw cap end. In the latter event the ready cooling of the mixture as it enters the needle will permit it to be retained in the barrel, or the needle may be immersed in sterile water as the paraffin is poured into the syringe, yet even if a few drops escape from the needle in the former method, no harm is done, as such loss amounts to nothing and helps to eventually fill the syringe evenly and free of air. If the mixture is drawn up into the barrel to the required height, more or less air enters, which must be removed by turning the syringe, needle up, and screwing up the piston rod until either the liquid or cylindrical thread of the cooled mixture appears. If the mixture is poured into the syringe the piston is slowly pressed into the barrel, thus allowing the air to escape along its sides if the mixture is set, or if warm the syringe is turned up and the piston screwed into place. As this is done the few drops of cooled paraffin will be forced from the needle before the air is exhausted. The screw is turned until the paraffin emerges evenly from the needle. The syringe must now be laid aside, or placed in sterile water of the temperature of the room, to allow the liquid within to set evenly and become uniform in consistency.