_Endo-tracheal anesthesia_ is by far the safest way for the administration of ether for any purpose. By means of the silk-woven catheter introduced into the trachea, ether-laden air from an insufflation apparatus is piped down to the lungs continuously, and the strong return-flow prevents blood and secretions from entering the lower air-passages. The catheter should be of a size, relative to that of the glottic chink, to permit a free return-flow. A number 24 French is readily accommodated by the adult larynx and lies well out of the way along the posterior wall of the larynx. Because of the little room occupied by the insufflation catheter this method affords ideal anesthesia for external laryngeal operations. Operations on the nose, accessory sinuses and the pharynx, apt to be attended by considerable bleeding, are rendered free from the danger of aspiration pneumonia by endotracheal anesthesia. It is the safest anesthesia for goiter operations. Endo-tracheal anesthesia has rendered needless the intricate negative pressure chamber formerly required for thoracic surgery, for by proper regulation of the pressure under which the ether ladened air is delivered, a lung may be held in any desired degree of expansion when the pleural cavity is opened. It is indicated in operations of the head, neck, or thorax, in which there is danger of respiratory arrest by centric inhibition or peripheral pressure; in operations in which there is a possibility of excessive bleeding and aspiration of blood or secretions; and in operations where it is desired to keep the anesthetist away from the operating field. Various forms of apparatus for the delivery of the ether-laden vapor are supplied by instrument makers with explicit directions as to their mechanical management. We are concerned here mainly with the technic of the insertion of the intratracheal tube. The larynx should be examined with the mirror, preferably before the day of operation, for evidence of disease, and incidentally to determine the size of the catheter to be introduced, though the latter can be determined after the larynx is laryngoscopically exposed. The following list of rules for the introduction of the catheter will be of service (see Fig. 59). RULES FOR INSERTION OF THE CATHETER FOR INSUFFLATION ANESTHESIA