_Question of Tubes, etc._--Once the trachea is opened, the next question is, How is the opening to be kept pervious? For the moment the handle of the scalpel is to be inserted in the wound, so as to stretch it transversely; this will probably suffice to allow of the escape of any foreign body. But where, to admit air, the wound is to be _kept_ open, how is this to be done? It used to be advised that an elliptical portion of the wall of the trachea be removed; this, though succeeding well enough for a time, was unscientific, as the wound always tended to cicatrise, and ended of course in permanent narrowing of the canal of the trachea. It may be necessary thus to excise a portion of the trachea, in cases where it is very intolerant of the presence of a tube. Such a case is recorded by Sir J. Fayrer of Calcutta.[132] Not much better is the proposal to insert a silk ligature in each side of the wound, and by pulling these apart thus mechanically to open the wound. This also is evidently a merely temporary expedient. Various canulæ and tubes have been proposed. The ones recommended by the older surgeons had all one great fault; they were much too small, and were many of them straight, and thus liable to displacement. The smallness of their bore was their greatest objection, and Mr. Liston conferred a great benefit on surgery by his insisting upon the introduction of tubes with a larger bore, and with a proper curve, so as thoroughly to enter the trachea. The tube ought to be large enough to admit all the air required by the lungs, without hurrying the respiration in the least. There is a mistake made in the construction of many of the tubes even of the present day; the outer opening is large and full, while for convenience of insertion the tube tapers down to an inner opening, admitting perhaps not one-half as much air as the outer one does. It must be remembered that for some days there is great risk of the tube becoming occluded, by frothy blood or mucus, especially in cases of croup, and in children. To prevent this a double canula will be found of great service, providing only that it be remembered that the inner canula, not the outer merely, is to be made large enough to breathe through, and that the inner should project slightly beyond the outer one. The inner one can thus be removed at intervals and cleansed, by the nurse, without any risk of exciting spasm or dyspnoea by its absence and reintroduction. _After-treatment._--The after-treatment of a case in which tracheotomy has been performed demands great care and many precautions. For the first day or two the constant presence of an experienced nurse or student is always necessary to insure the patency of the tube. The temperature of the room should be equable and high, and it seems of importance that the air should be kept moist as well as warm by the use of abundance of steam.