The anæsthetics used during the extraction of teeth may be divided into two classes, viz.:--general and local. It is not proposed to make any allusion to the methods of administering general anæsthetics, as they hardly fall within the scope of this volume. There are, however, a few points which the operator should bear in mind when employing them and which may with advantage be briefly dwelt upon, but before considering these, a word or two may not be out of place with regard to the choice of the anæsthetic. In dental practice three agents are generally used, nitrous oxide alone or in combination with air or oxygen, ether and chloroform. In the very large majority of dental operations nitrous oxide is to be preferred to ether and chloroform, and possesses the great advantage over them of being practically safe. In addition, the administration of nitrous oxide occupies a shorter period, and the recovery is rapid and complete. Within the last few years, combinations of nitrous oxide with oxygen and with air have been introduced by Dr. Hewitt and Mr. Rowell respectively, and both combinations possess advantages over nitrous oxide used alone. _The advantages of nitrous oxide and oxygen over nitrous oxide alone are_:-- (1) The anæsthesia is quieter. (2) The mucous membranes of the mouth do not swell to the same extent, and the operator therefore gains a clearer view of the tooth. (3) The period of anæsthesia is lengthened, perhaps by only a few seconds, but the quieter condition of the patient assists indirectly in prolonging the period for operating. _The advantages of nitrous oxide with air over nitrous oxide alone_ are somewhat similar to those of nitrous oxide and oxygen, though less marked. _For operations requiring a long anæsthesia_, such as the extraction of a difficult third molar, ether should be used, the administration being commenced with nitrous oxide. In such cases many operators prefer to use chloroform, but the regular employment of this agent in dental surgery is to be severely condemned, and the cases are rare indeed in which its use is called for. A most careful inquiry into this important subject has been made by Dr. Hewitt, and the results of his work were communicated in an exhaustive paper published in the _Journal of the British Dental Association_ for November, 1895, which is well worthy the perusal of all those who are in the habit of administering chloroform. Whenever a general anæsthetic is given for the removal of teeth, two people should always be present, one to confine his attention solely to the administration of the anæsthetic, the other to the removal of the tooth, as it is impossible for one person to operate and at the same time to observe the condition of the patient during the anæsthetic period. This rule should be strictly adhered to.