Analgesia is the first stage of anesthesia--the "twilight zone" of approaching unconsciousness--in which the sense of pain is greatly dulled or entirely lost, while even that which is experienced is not remembered. It seems to the authors that "gas" is the ideal drug for producing this condition whenever it is necessary, as nitrous oxid is the most volatile of anaesthetics, acts most quickly, and its effects pass away most rapidly, while its administration is under the most perfect control--it may be administered with any desired proportion of oxygen--and may be discontinued on a moment's notice. It is practically free from danger even when continued as an analgesic for several hours. Nitrous oxid never causes any serious disturbance in the unborn child, as chloroform sometimes does when used too liberally. EFFECTS OF NITROUS OXID It will not be necessary to compare the favorable and unfavorable claims for nitrous oxid as we did the contentions for and against "twilight sleep." Whatever service "laughing gas" or "sunrise slumber" can render the cause of obstetrics we can accept, knowing full well that, in competent hands, it can do little or no harm; and this we know from the facts herewith recited and from the further fact that we have gained a wide experience with this agent in the practice of both dentistry and surgery. In a general way, the influence of "sunrise slumber" on mother and child may be summarized as follows: 1. It can accomplish its purpose--can quite satisfactorily relieve the mother of severe pain--when employed as an analgesic. It is not necessary to administer the gas to the point of anesthesia except at the height of suffering at the end of the second stage of labor, when the head of the child is passing through the birth canal. 2. This method can be stopped at any moment--the patient ran be brought out from under its influence entirely and almost instantaneously. It is not like a hypodermic injection of a drug which may exert a varying and unknown influence upon the patient, and which, when once given, cannot be recalled. 3. It is a method which may be used in the patient's home just as safely as in a hospital; the only drawback being the inconvenience of transporting the gas-containing cylinders back and forth. This is even now partially overcome by the improved combination gas and oxygen form of apparatus which has been devised. 4. The administration of nitrous oxid analgesia or anesthesia does not interfere with or lessen the uterine contractions or expulsive efforts on the part of the mother--at least not to any appreciable extent. 5. Just as soon as a severe uterine contraction--attended by its severe pain--begins to subside, the gas inhaler is immediately removed, and in a few seconds the patient is again conscious. It is not necessary to keep the patient continuously under the influence of the drug, as in the case of the scopolamin-morphin method of "twilight sleep."