Looking at the subject from the anatomical side, the writer is bound to confess that an argument _a priori_ would have led him to expect extraction to have been by far the more painful of the two procedures, both at the time and during the early hours of convalescence, although much has been made by early writers of injury to the retina and to the sensitive ciliary body, and of the extensive damage done by the needle during a couching. We know, however, that injury to the retina does not produce pain; and we are also well aware of the extreme susceptibility of the cornea to pain. Surely the extent of damage inflicted on sensitive structures is, as a rule, much greater in an extraction than it is in a couching. How then are we to explain the dread with which surgeons, in the days of couching, looked forward to the suffering and vomiting which sometimes followed the operation? In answer to this question the following suggestions are put forward. The pain of the first twelve hours is to be sharply differentiated from that which begins on the second or third day, always remembering, however, that, though the causes are different, the one may run into the other. The early pain may be ascribed (1) to injury to the nerves of the ciliary body and iris, especially when the laceration of those structures is considerable, as our clinical experience and our specimens alike show it sometimes is; (2) to hæmorrhage from the vessels of the ciliary body, the iris, the choroid or the retina: such hæmorrhage may produce pain in two ways--(_a_) by dissecting up sensitive structures, and (_b_) by increasing the tension of the eye; and (3) to the rapid production of early glaucoma. There are several ways in which we may conceive that such a glaucoma might be produced. We have already mentioned the possibility of hæmorrhage. Then we have to remember that, in the course of this operation, the anterior portion of the vitreous body is often extensively interfered with. It is conceivable that a forward movement of this part may close the angle of the chamber, and so interfere with excretion. Again, when the lens is forced back on the vitreous body, and the anterior hyaloid layer remains unbroken, we sometimes find it acting as a wedge, pushing the base of the iris forward, and thrusting the hyaloid membrane backward. The latter action must press on the vitreous body, and so make it bulge at other parts of the circumference of the eye, thus tending to close the angle of filtration over such areas. It is obvious that the pressure of the lens on the iris base will directly close the sinus locally to a greater or less degree. A point that we must never lose sight of is that the very great majority of these patients are in the glaucoma period of life, and with a certain number of them very little alteration of the _status quo_ is required to precipitate an attack of pathological high tension. If we take all these factors into account, and especially if we bear