Celsus describes very accurately the operation of catheterism. The tube or catheter, he says, should be made of copper, and the male catheter ought to be somewhat bent, smooth, and neither too large nor too small for the passage. The length of the largest male catheter should be 15 inches, of the middle-sized 12, and of the smallest 9; the largest female catheter should he 9, and the smallest 6 inches. The patient is to be laid on his back, and the surgeon standing by his right side, and holding the penis in his left hand, is to introduce with his right the catheter into the urinary passage; and when it reaches the neck of the bladder, the instrument along with the penis is to be bent downwards and introduced into the bladder. When the water is evacuated the catheter is to be extracted. The female passage, he remarks, is shorter, and is discovered by a sort of mammary protuberance above the vagina, by which he evidently means to describe the clitoris. The operation, he adds, in this case is less difficult. (vii, 26.) The operation is mentioned by Aëtius and other of the Greek authorities, but none of them describe it fully but Paulus. Albucasis recommends a catheter made of silver. His account of the operation is evidently borrowed from our author. He describes and gives a drawing of an instrument for throwing injections of oil and water into the bladder when inflamed. It is a tube of silver or copper having the bladder of a ram attached to it. (Chirurg. ii, 59.) Avicenna and Serapion mention the operation but do not describe it minutely. Haly Abbas directs us to make the patient sit and to pour warm water and oil upon the penis. This is evidently recommended with a view of producing relaxation. The ordinary steps of the operation are very properly described by him. (Pract. ix, 45.) Rhases gives a fuller account of catheterism, and all the circumstances connected therewith, than any other ancient author. He very properly forbids the catheter to be introduced when the retention arises from inflammation at the neck of the bladder. (Ad Mansor. ix, 73.) He first gives Antyllus’s description of the operation, which is very accurate, but similar to our author’s. He recommends us, before attempting the introduction of the instrument, to put the patient into a warm bath, or to apply hot fomentations to the parts. He then directs us to lubricate the instrument with oil or thick mucilage, and to introduce it into the passage until it arrives at the under extremity of the penis, when it is to be gently pushed upwards in the direction of the navel, turning it to one side or another according as it encounters obstruction. He states that it is best to have the openings of the catheter in its sides as they are less likely to be obstructed by clots than when in the extremity. He also mentions that he was sometimes in the practice of using a ductile instrument of lead which accommodated itself to the passage.