The technique of using the metal catheter in the male is the same as that of introducing a sound. A lubricant is necessary for the easy introduction of the instrument, and a sterilized ointment or oil will serve the purpose. Olive oil, mixed with iodoform, as often used, is not sterile. The hands of the operator should also be clean, and no part of a clean instrument should be allowed to come into contact with any portion of the patient’s surface. On this account the parts exposed should be covered with sterile towels. The catheter being intended to afford relief with the least amount of discomfort, a smaller instrument may be used than would be inserted were it meant for the dilatation of a stricture. Occasionally, and in a sensitive patient or hyperesthetic urethra, a little cocaine solution may be used to advantage, especially if force or pressure need be made in order to overcome spasm of the cut-off muscle. The metal instrument is too rigid in some cases, while the gum catheter is too flexible. Under these circumstances, the silk instrument may be used. If the tip of the instrument be kept close to the floor of the urethra it will rarely catch in any fossa or lacuna, particularly if the size has been correctly chosen. When apparent obstruction occurs at the triangular ligament the instrument should be withdrawn a little, tilted differently, or lifted a little so that it is made to hug the roof of the urethra rather than to press upon its floor. By a little manipulation of the end of the instrument any obstruction at the neck of the bladder may also be overcome. A sudden depression of the outer end as the catheter reaches this part, or a little pressure by the finger of the disengaged hand in the perineum, will give much help. It is well, occasionally, to introduce one finger into the rectum in order that by it the instrument may be better guided along its course. Only in cases where there has been previous disease or where unsuccessful attempts have already been made to pass an instrument will much real difficulty be found; that is, only in those already suffering from stricture, or from enlarged prostate with the difficulties which it affords, will one have to resort to manipulation requiring more than ordinary dexterity. In some of these cases even the expert is likely to meet with difficulty, rarely with absolute disappointment. Should it be impossible to empty a distended bladder with a catheter _suprapubic puncture_ with the _aspirator needle_ should be made. When difficulty is experienced it is enhanced by spasm of the deep muscles, as a reflex from the soreness produced by repeated efforts and by hemorrhage. Hemorrhage from this source is rarely of serious character and quickly ceases. In certain instances where it is aggravated much can be accomplished by leaving the catheter _in situ_ for a few hours, or even for two or three days.