and should be withdrawn gradually, not hastily, after the capsule has been rent: but the operator should not begin to withdraw it until this object is accomplished. By these precautions the aqueous humour is retained, and the pupil preserves its dilatation, till the cataract is set at liberty; and the prolapsus iridis, which in neglect of them will sometimes occur, is effectually prevented. Where the capsule is opake, it generally escapes with the lens, and not a vestige of it can be seen within the pupil. In operating upon the adult after this manner, the surgeon should be careful to ascertain that the cataract is either fluid, flocculent, or of the softest caseous kind. If he should find that he has mistaken a firm for a soft cataract, the section of the cornea must be completed. The point of the knife should not penetrate the cornea at a less distance than one line from its margin, in any operation for which it is used.* If the iris should prolapse, it must be gently replaced with the back of the scoop. This may be done, if unfortunately it has not been sooner discovered, even as late as three or four days after the operation, as the adhesions are recent, and will yield to gentle pressure; upon the evacuation of the aqueous humour, the iris resumes and retains its place. But if the iris prolapses after the patient is bandaged, and put to bed, it takes place during the period of the secretion of the aqueous humour, being caused by the accumulation of this fluid behind it, which protrudes its overstretched fibres in the form of a little sac or bag between the lips of the wound, before the process of union is completed.

As it is of importance to the recovery of the pupil, as well as the healing of the wound, and the prevention of an acute inflammation, from the irritation which this protrusion causes, that it should be as early as possible replaced, I never permit the eye, in which from any cause the iris has prolapsed at the time of the operation, to remain unexamined on the second day, by which time the humour is secreted, for the purpose of ascertaining that the pupil is shapely, and the cornea healing. No evil results from this examination; but as the accident is

* The disposition to prolapsus iridis is increased, if not induced, by carrying the section too near to the margin of the cornea, by which its basis is deprived of support.

VOL. VI.

2 U

No. 23.

liable to occur in this interval, and cannot be redressed with equal ease or advantage at a later period, if at all, it should in no case be omitted.

I embrace the opportunity which this paper presents, of making a few remarks on the operation of extraction, as applicable to cataracts of firm consistence, in the hope that they may be useful to those who undertake it. It is quite unnecessary to offer a systematic description of its stages, after the copious and valuable instructions which the profession have received upon the subject from Richter, the Wenzels, and Mr. Ware. To convey an idea of the importance of performing this operation in that manner which admits of the removal of the cataract with facility, I need only remark, that I have never seen any extraordinary or untoward inflammation ensue, where the operation was so conducted. On the other hand, that I have scarcely ever known an instance of difficulty in the removal of the lens, in which the object of the operation was not in a great degree frustrated, or which was not succeeded by considerable inflammation, and consequent disorganization and deformity. The result being thus influenced by the circumstances of the operation, it becomes important to know from what cause the extraction is rendered difficult, and what the ill consequences are of which it is productive.

The cause of difficult extraction is an insufficient section of the cornea; the ill effect of it is the implication of the iris in the wound. I was formerly at a loss to know, why, after a tolerably well formed section of the cornea, and a sufficient aperture of the capsule, the lens showed no disposition to advance, upon applying a moderate pressure to the globe. By increasing the pressure in such a case, I found that the capsule of the vitreous humour yielded, and a portion of that humour escaped; the cataract having lost its support, sunk away from the pupil, and every introduction of the curette, hook, or scoop, increased the discharge. At other times, the lens advanced upon pressure of the globe, as it were reluctantly, became wedged in the section of the cornea, and was, by the continuance of the pressure, gradually but difficultly squeezed out.

In the first of these cases the section was not only not of extent sufficient for the mechanical expression of the lens, but the

divided portion of cornea formed so small a part of its circumference, that its resistance was but slightly diminished; and, except that the aqueous humour was evacuated, it in effect retained its integrity. In the second case the lens advanced, because this resistance was either greatly diminished or taken away, although the section was demonstrated to be barely sufficient for the escape of the lens. When I speak of the resistance of the cornea to the escape of the lens, I refer to its figure and its relation to the pupil through which the lens is to pass. It will be understood by observing the difference of effect produced by sections of the cornea, of the same extent, opposite to and at the greatest distance from the pupil. It is evident, that the situation of the section will be more favourable to the escape of the lens, the nearer it approaches to the pupil. I have seen some dexterous operators perform a straight section which just cleared the inferior margin of the pupil. Now if a crescentic section of the same extent were made at the inferior margin of the cornea, the extraction of the cataract could not be accomplished. The cornea being in the former case divided at its greatest diameter, its resistance is taken off, and therefore the lens will readily advance through a sufficient aperture of its capsule, although the wound of the cornea is obviously too confined; but in the latter, the cornea retaining two-thirds of its circumference entire, the effect of pressure is only to preserve the contact between the iris and cornea, which took place on the evacuation of the aqueous humour, and to render the cornea a perfect valve upon the aperture of the pupil. That this is the effect it has, is demonstrated by a common occurrence, viz. the bulging of the iris at the inferior border of the pupil. The lens, upon pressure of the globe, being unable to pass the pupil, pushes this membrane before it, where it has lost its support by the division of the cornea. The operator, observing this, supposes that the capsule of the lens is imperfectly opened, and it may be so; but if it were removed entire from the face of the lens, the same thing would happen, and

* I am far from meaning to commend a section parallel to the lower border of the pupil; the fact is merely stated, that the reason may appear why the section of a proper situation and figure should also be of a proper extent.

continued or increased pressure have no other effect than that of continuing and increasing the distension and protrusion of the iris. If the section of the cornea be equal to its semicircumference, the effect of pressure is to dilate the pupil, and permit the escape of the lens. The iris has been supposed in some cases to resist the passage of the lens, and it is probable the opinion may have arisen from a circumstance similar to that which I have endeavoured to explain; but the truth is, that the iris is perfectly passive, and never, in my belief, forms an impediment to the passage of the lens, where it has lost the support of the cornea.

To give the section the situation and extent required, it should describe a curve similar to that of the margin of the cornea, equi-distant about one line from the sclerotic, commencing at the same distance above the transverse diameter of the cornea, and terminating a little below that diameter on the opposite side.

Incised wounds of the cornea are well disposed to heal by the adhesive inflammation, and the structure of that membrane is favourable to the close and complete apposition of their edges. A portion of the lymph uniting the cut surfaces is generally effused between the conjunctiva and cornea to a small distance beyond them, but this is in a little time absorbed, and the cicatrix becomes but faintly visible, forming a very delicate opake line. But if the lens has been forcibly delivered by a small section, the iris is compressed and bruised in its passage, and instead of recovering its plane, the lower border of the pupil falls between the edges of the wound, and partakes of the inflammation raised to heal it. It does not actually prolapse, but, by its intervention of the edges, forms a part of the cicatrix, so as to elevate the flap, and distort the figure of the cornea, and by its co-adhesion with the latter to render it more or less extensively opake from the section upwards. This tendency of the iris to inflame and unite with the cornea is universal, where it has been stretched, compressed, or bruised by the lens in its passage; the injury is often aggravated by the use of instruments to open the capsule and extricate the lens, which entangle in the iris, or abrade the cornea on its interior surface, so that the opacity eclipses the pupil; but where the iris has

been bulged and protruded by the lens during the operation in the manner before described, the prolapsus which ensues is sometimes of such magnitude as to draw the upper segment of the pupil into the wound, and thus completely to close it and obliterate the anterior chamber.

I have now pointed out, as faithfully and as clearly as I am able, what has appeared to me to be the principal cause of the difficult extraction of the cataract, and its consequences. The means of preventing it are sufficiently obvious; and it will be sincerely gratifying to me, if these observations should spare others the painful necessity of occasionally witnessing evils which they might have prevented, but are unable to relieve.

It is difficult in speaking of an operation, in the conduct of which so many minute circumstances demand attention, to refrain from entering into detail. On such points, however, few persons can be instructed with advantage, for all are competent, and in the course of their experience, compelled to form a judgment of their own; which will be more readily and more accurately formed by an appeal to practice than to books. One observation only, I will add, of general importance to the perfection of the operation. Some surgeons simply incise the capsule near to the lower border of the pupil, for the egress of the lens, and leave the remainder of it entire, occupying the centre of the pupil, in the expectation that it will remain transparent. This is not realized by the event; the capsule invariably turns opake after the escape of the lens, and renders the operation, for a time at least, imperfect. Whatever operation for the cataract is selected, whatever instrument is employed for the aperture of the capsule, it is essential that the central portion of this membrane should be extensively lacerated. To conclude, the operation of extraction by the section of the cornea in its semi-circumference, is the only one properly adapted to the firm caseous and hard cataract. Although pregnant with fortuitous and unexpected circumstances, embarrassing to surgeons, who have not enjoyed frequent opportunities of performing it, it offers no difficulty which coolness and perseverance will not soon overcome; and when executed with the confidence and adroitness which experience will infallibly give, it is, whether considered in design or in effect, one of the most.