Celsus lays it down as a rule, that when the suffusion is small, immovable, and of the colour of sea-water, or of shining iron, and if a small degree of light can be perceived at the side, there is reason to hope well of the case. He forbids us to operate until the disease has attained a proper consistence. He directs us to place the patient opposite the operator, who is to sit on a higher seat, while the patient’s head is firmly held by an assistant. The sound eye is to be previously covered up with wool. If the left eye is affected the operator must use his right hand, and vice versa. A needle which is sharp and not too slender is to be passed direct through the two coats at a place intermediate between the temporal angle and the black of the eye, and towards the middle of the cataract. When the needle has perforated far enough, which is readily known by the absence of resistance, it is to be gently turned so as gradually to remove the cataract below the region of the pupil, and this object being attained it is to be strongly pressed to the lower part. If it remain there the operation is completed; but if it return it is to be cut and torn by the needle into many pieces, in which state they are easier depressed, and prove less troublesome. The needle is then to be drawn out direct, and soft wool smeared with the white of an egg, and other anti-inflammatory applications are to be used. Quiet, restricted diet, and soothing treatment will be proper. Galen, in his ‘Ars Medica’ alludes to the operation, but does not describe it. Paulus is the only Greek author who describes the operation. Sextus Platonicus, however, just mentions that the diseased part is sometimes to be depressed with a specillum. (De Medic. ex Animalibus.) Mesue describes the operation of couching briefly, but nearly in the same terms as our author. He directs us to put the patient upon a spare diet, and to bleed him before the operation. He recommends us to be careful to depress the cataract (aqua) properly. Albucasis describes the operation of Paulus very minutely, and gives drawings of the couching-needles, called by him almagda. The instrument is to be passed down into the eye to as great a space as the pupil of the eye is distant from the end of the black part called the corona. He says nothing of tearing the cataract into pieces when it proves difficult to depress. He mentions that he had heard of a certain oculist who, it was said, sucked out the cataract through a small tube. He adds, however, that he had never seen any person who performed this operation, nor had read anything about it in the works of the ancients. Avenzoar briefly mentions that when a cataract cannot be got discussed it must be depressed. He gives directions to press it well down, but says nothing about tearing it into pieces. He recommends retirement, abstinence, and rest afterwards.