The agents used are chloroform, ether and nitrous oxid gas, while what is popularly called “twilight sleep” is produced, completely or in a modified degree, by the hypodermic administration of scopolamin and morphine. =Chloroform.= Of these various drugs chloroform is apparently the anesthetic most widely used in normal obstetrics. Its advantages are that it is easy to give; quick in its action and is followed by little or no nausea or other ill effects. For some reason, as yet not explained, the woman in labor enjoys a certain amount of immunity against chloroform poisoning, but this tolerance exists only during labor as the puerperal woman is subject to the same dangers as any other individual. Chloroform is not usually administered until the patient is well along in the second stage, or until the head may be felt through the perineum, or is in sight. The patient’s face should be oiled and protected with a towel or gauze folded across her brow, mouth and chin to prevent burns that might follow the inadvertent dropping of chloroform on her face. With the beginning of a pain, a few drops are poured on the inhaler which is held about an inch from the face to give a free admixture of air, and the patient is told to breathe in deeply. (Fig. 103.) The inhaler is removed as soon as the pain subsides, but reapplied as soon as another pain begins. The patient retains consciousness and is able to talk under this degree of anesthesia, but her suffering is greatly relieved. It has the advantage, also, of lessening the danger of perineal tears, as the accoucheur has better control of the delivery when the patient lies quietly than when she tosses violently about the bed, and a tear resulting from the sudden delivery of the head at the height of a pain may in this way be averted. This light, intermittent anesthesia, now so widely used, is called obstetrical anesthesia or anesthesia _à la reine_, after Queen Victoria, upon whom it was first employed at the birth of her seventh child, in 1853. When the perineum is distended to its maximum, obstetrical anesthesia is not always sufficient, and complete anesthesia may be employed; but even this requires very little chloroform. Under ordinary conditions, the anesthesia is discontinued as soon as the child is born, for unless there is an extensive tear, the patient is sufficiently anesthetized to permit of a perineal repair and the delivery of the placenta. Chloroform is not often given early in labor because of the general belief that its free or prolonged use lessens the force and frequency of uterine contractions, thus prolonging labor, and also may unfavorably affect the child. But small doses seem to stimulate rather than retard contractions, and by having her pain relieved, the patient is prompted to make greater effort to use her abdominal muscles, an end greatly to be desired.