THE Fistula in Ano, without any regard to the strict Definition of the Word, is generally understood to be an Abscess, running upon, or into the Intestinum Rectum; though an Abscess in this Part, when once ruptured, does generally, if neglected, grow callous in its Cavity and Edges, and become at last, what is properly called a Fistula.

That the Anus is so often exposed to this Malady, in any Crisis of the Constitution, is chiefly ascribed to the depending Situation of the Part; but what very much conduce to it likewise, are the great quantities of Fat surrounding the Rectum, and the Pressure the Hæmorrhoidal Vessels are liable to, which being sustained upon very loose Membranes, will be less able to resist any Effort, that Nature shall exert, to fling off a Surcharge; and from one Step to another, that is, from Inflammation to Suppuration, lead on to the Distemper we are treating of. That the Fat is the proper Subject of Abscesses, may be learned from an Inflammation of the Skin affecting the Membrana Adiposa, and producing Matter there; in which Case, a Suppuration frequently runs from Cell to Cell, and in a few days, lays bare a great quantity of Flesh underneath, without affecting the Flesh itfelf: Nay, I think it may be doubted, whether in those Abscesses which are esteemed Suppurations of the Muscles, the Inflammation and Matter are not absolutely first formed in this Membrane, where it is insinuated in the Interstices of their Fibres.

The Piles, which are little Tumours formed about the Verge of the Anus, immediately within the Membrana interna of the Rectum, do sometimes suppurate, and become the Fore-runners of a large Abscess; also external Injuries here, as in every other part of the Body, may produce it; but from whatever Cause the Abscess arise, the manner of operating upon it will be according to the Nature and Direction of its Cavity.

If the Surgeon have the first Management of the Abscess, and there appear an external Inflammation upon one side of the Buttock only; after having waited for the proper Maturity, let him with a Knife make an Incision the whole length of it; and in all probability, even though the Bladder be affected, the Largeness of the Wound, and the proper Application of Dossils lightly pressed in, will prevent the Putrefaction of the Intestine, and make the Cavity fill up like Imposthumations of other Parts.

If the Sinus be continued to the other Buttock, almost surrounding the Intestine; the whole Course of it must be dilated in like manner; since in such spongy cavities, a Generation of Flesh cannot be procured but by large Openings; whence also, if the Skin is very thin, lying loose and flabby over the Sinus, it is absolutely necessary to cut it quite away or the Patient will be apt to sink under the Discharge, which in the Circumstance here described, is sometimes excessive. By this Method, which cannot be too much recommended, it is amazing how happy the Event is likely to be; whereas from neglecting it, and trusting only to a narrow Opening, if the Discharge do not destroy the Patient, at least the Matter, by being confined, corrupts the Gut, and insinuating itself about it, forms many other Channels, which running in various Directions, often baffle an Operator, and have been the cause of a Fistula being so generally esteemed very difficult of Cure.

Here I have considered the Imposthumation as possessing a great part of the Buttock; but it more frequently happens, that the Matter points with a small extent of Inflammation on the Skin, and the Direction of the Sinus is even with the Gut: In this case, having made a Puncture, you may with a Probe learn if it has penetrated into the Intestine, by passing your Finger up it, and feeling the Probe introduced through the Wound into its Cavity; though for the most part, it may be known by a Discharge of Matter from the Anus. When this is the state of the Fistula, there is no Hesitation to be made; but immediately putting one Blade of the Scissars up the Gut, and the other up the Wound, snip the whole length of it. This Process is as adviseable when the Intestine is not perforated, if the Sinus is narrow, and runs upon or very near it; for if the Abscess be tented, which is the only way of dressing it while the external Orifice is small, as I have here supposed, it will almost certainly grow callous; so that the surest means of Cure, will be opening the Gut, that proper Applications may be laid to the Bottom of the Wound. However it should be well attended to, that some Sinuses pretty near the Intestine, neither run into nor upon it, in which case they must be opened according to the course of their Penetration. There are abundance of Instances, where the Intestine is so much ulcerated, as to give free issue to the Matter of the Abscess by the Anus; but I believe there are none where there is not by the Thinness and Discolouration of the Skin, or an Induration to be perceived thro' the Skin, some mark of its Direction; which, if discovered, may be opened into with a Lancet, and then it becomes the same Case as if the Matter had fairly pointed.

If the Sinuses into, and about the Gut, are not complicated with an Induration, and you can follow their Course; the mere opening with Scissars, or a Knife guided on a Director, will sometimes suffice; but it is generally safer to cut the piece of Flesh surrounded by these Incisions, quite away, and when it is callous absolutely necessary, or the Callosities must be wasted afterwards by Escharotick Medicines, which is a tedious and cruel Method of Cure.

When the Fistula is of long standing, and we have choice of Time for opening it, a Dose of Rhubarb the Day before the Operation, will be very convenient, as it not only will empty the Bowels, but also prove an Astringent for a while, and prevent the Mischief of removing the Dressings in order to go to stool.

It sometimes happens that the Orifices are so small, as not to admit the Entrance of the Scissars; in which case, Sponge-tents must be employed for their Dilatation.

In performing these Operations on the Anus, I do not think, in general, any Instrument so handy as the Knife and Scissars; almost all the others which have been invented to facilitate the Work, are not only difficult to manage, but more painful to the Patient: However, in those Instances where the Fistula is very narrow, and opens into the Intestines, just within the Verge of the Anus, the Syringotomy may be used with Advantage: But where the Opening into the Gut is high, it cannot be employed without giving great Pain. I do not caution against cutting the whole Length of the Sphincter, Experience having shewn it may be done with little Danger of an Incontinence of Excrement; and in fact the Muscle is so short, that it must generally be cut through in Dilatations of the Intestine. The worst Species of Fistula, is that communicating with the Urethra, and sometimes (thro' the Prostate Gland) with the Bladder itself. This generally takes its rise from a former Gonorrha, and appears externally first in Pærineo, and afterwards increasing more towards the Anus, and even sometimes into the Groin, bursts out in various Orifices, thro' the Skin, which soon becomes callous and rotten; and the Urine passing partly thro' these Orifices, will often excite as much Pain, and of the same kind, as a Stone in the Bladder.

This Species of Fistula taking its rise from Strictures of the Urethra, is only managable by the Bougie: for so long as the Urethra is obstructed, the Cure of the Fistula will be imperfect; but if the Canal be opened by this Application, it is amazing what obstinate Indurations and foul Sinuses will in consequence disappear; tho' there are some so callous and rotten, as to demand the Knife and skilful Dressings, notwithstanding the Urethra should be dilated by the use of Bougies.