Many different methods have been recommended for the dilatation of the tracheal wound and to assist the introduction of the canula. The dilator (Trousseau) which has been mentioned surely answers all purposes, and is simple and easily used. An ordinary dressing forceps will likewise do the work if introduced closed and afterward opened. More complicated procedures are unnecessary. Thyro-cricotomy requires that the superficial incision be so made over the larynx that the thyro-cricoid space shall lie in the centre of one, about two inches long, made in the median line. Following now the dissection just described, the thyro-cricoid membrane is easily reached and quickly seen as soon as the sterno-hyoid muscles are retracted. It should then be divided transversely close below the lower edge of the thyroid cartilage, the wound dilated, and the tracheotomy-tube slipped into place. {155} Inferior tracheotomy demands that the external incision be free. In children, and in adults with a short neck, it should extend from the cricoid cartilage to just above the sternum. The subsequent steps of the operation are as for superior tracheotomy, with but slight differences. The anterior jugular veins may come into view, but can generally be avoided. If they are joined by a transverse branch, this is necessarily cut through after being doubly ligated. After the thyro-hyoid muscles are separated, the rings of the trachea are much less distinctly felt at first than in superior tracheotomy, being covered by more connective tissue and numerous veins. These inferior thyroid veins, especially if large, are the great obstacle in the way of this operation, and much care is necessary in order to avoid them, which should be done if possible. The lower edge of the isthmus of the thyroid gland, which presents to a variable extent above in the wound, does not, as a rule, offer any obstruction. The thymus gland present in infants is easily pulled downward and out of the way. The trachea at length fairly exposed and all bleeding controlled, the left fore finger of the operator is placed in the lower angle of the wound to securely protect the large blood-vessels here located, and the incision made through some three tracheal rings from below upward. It may happen that in either a superior or inferior tracheotomy no time will be allowed for careful and slow dissection as here described. In such instances Durham advises that the surgeon grasp the trachea between the fore finger of his left hand on the left side and the thumb on the right, and make uniform, steady, deep pressure, thus firmly securing it and at the same time protecting the large vessels of the neck. The fingers thus placed are not to be moved until the trachea is reached, which is accomplished by rapid incisions confidently made. The pressure of the fingers causes the wound to gape and the trachea to advance. The latter reached, it is caught by the tenaculum and the operation completed as before described.