Paracentesis should be done early in infants and in specific fevers. In the former case even a slight middle-ear inflammation may give rise to all the cardinal symptoms of meningitis, which frequently subside rapidly as the result of simple paracentesis; in the latter, there may be rapid destruction of the drum, which a timely incision may possibly prevent. (ii) _In middle-ear catarrh with exudation._ Paracentesis is justifiable in order to remove the secretion, if the hearing does not improve after a month’s treatment, owing to the existence of exudation within the tympanic cavity. (iii) _As a preliminary to intratympanic operations._ =Operation.= The auricle and surrounding parts are surgically cleansed (see p. 309), the preliminary toilet, if possible, being carried out at least half an hour before the operation is performed. Although apparently a trivial matter, it is of the utmost importance to render the auditory canal as aseptic as possible in order to prevent secondary infection of the tympanic cavity from without. It is wiser to give a general anæsthetic, such as gas and oxygen, as the pain of the operation may be intense. If this is refused, local anæsthesia by Gray’s solution (see p. 310) or by a subcutaneous injection of cocaine and adrenalin may be employed. In infants an anæsthetic is not necessary. The patient may be sitting up or lying down. If a general anæsthetic has not been given, the patient’s head must be held firmly by an assistant in order to prevent sudden movement. The surgeon works by reflected light in order to obtain a clear view of the tympanic membrane. The point of election for the incision is through the posterior part of the membrane, excepting when it is obvious from the bulging and appearance of the membrane that the incision must be made in the anterior inferior quadrant. The incision is made by means of a paracentesis knife, which is shaped like a tiny bistoury set at an angle to its handle (Fig. 187). The double-edged spear-shaped knife is now seldom used, as with it there is a tendency to puncture rather than to incise the membrane.