Called also archos, cuius, hedra, podex cyr-seon, cyssaros; and in Hippocrates, cathedra; some name it perin. It is the lowest part of the intestinum rectum, commonly called the fundament. The extremity of the rectum contracts into a narrow orifice, the sides of which are disposed in close circular folds. This is called sphincter ani, which see. It hath several muscles belonging to it, some of which surround it as sphincters; the rest arc broad, and fleshy planes inserted in it, and which, being inserted likewise into other parts, sustain it in its natural situation, and restore it when disturbed by the force necessary for excluding the faeces: the latter muscles are termed levatores ani. Two ligaments belong to the anus, viz. the ligamentum cu-tancum ossis coccygis, and the ligamentum pubis in-terosseum. See Ligamentum. The nerves of the anus and its muscles are from the ganglions of the plexus hypogastricus, the inferior cord of both the sympathetici maximi, and the common arch of the extremities of both cords. The margin or edge of the anus is a continuation of the skin and epidermis, with the internal coat of the intestinum rectum. This part is extremely vascular; and a troublesome haemorrhage, when the operation is performed for the fistula in this part, often ensues.

The anus is subject to many disorders, and they arc-generally somewhat difficult of cure, because of the irritability of the part, which subjects it to receive fresh injury from many accidents. Aetius observes, that astringents which are acrid, the sensibility of the anus cannot bear; and that astringents which are not acrid, such as metals, should be applied. On the diseases of this part, see Aetius, Celsus, P. AEgineta, Turner, Heis-ter, and Wiseman. See also Rectum. Discharges of wind from the anus are called crepitus.

Excrescences about the Anus.

Various excrescences are found about the verge of the anus; many of these, produced merely by relaxation and safely removeable, are unattended with pain, or any disagreeable discharge, and arc single or distinct, whatever their number be. In removing them, the ligature, to avoid a troublesome haemorrhage, is preferable.

When they discharge a bloody fluid matter and are painful, they are also generally in clusters, or not distinct; and for the most part disposed to be, if not already become, cancerous. Mr. Pott observes, that in cancerous cases of this kind there is rarely a single excrescence, but the gut is for the most part surrounded with them; and if a finger is passed into the intestine, those tumours produce the idea of pushing the finger into a rotten pomegranate. Beyond palliation, no relief can be afforded.

The Anus imperforated.

Sometimes children are born with a membrane across the anus, which obstructs the discharge of the excrements. If the situation of the anus cannot be discovered in consequence of the thickness of the superfluous substance which closes it up, a cure cannot be expected; for much, if not the whole rectum, is closed up or wanting. If the case admits of a cure, the situation of the anus will be seen by a prominence, or by a little hollow.

This accident is generally spoken of as if always circumstanced alike. Mr. Pott very judiciously divides it into four classes. 1st. Where there is no mark or vestige of an anus perceptible: in this case the rectum is as it ought to be until it arrives at the bulb of the urethra; from this there is no intestine, and no anus externally. If the rectum reaches too near the part where the anus should be, the impulse of the faeces against the skin will discover where a perforation may be made; but if no such impulse is to be felt, when the child coughs or cries, relief cannot be afforded. 2d. Where there is a circle or mark in the skin which points out where the anus should be: in this instance the difficulty is not considerable. However, it may be proper to add, that the perforating instrument should be introduced in the direction of the os sacrum; if it passes forward, the bladder, or the uterus, or both, may be injured; if it is to be introduced far up, to divide a membranous obstruction in the rectum, in cutting it should be moved not upward, but from side to side; thus you avoid wounding the prostate gland, or the vesiculae stminales, and perhaps the neck of the bladder. 3d. Where there is a well formed anus, and perforated, but no communication with the intestinal tube, from the rectum being imperforated, if the child is not duly attended to, it dies in great agonies. If an infant hath had no stools during the first or second day after its birth, a finger should be dipped in oil, and thrust up the rectum, to discover whether any obstruction is there. 4th. Where there is neither anus nor rectum, but the intestinal canal terminates in the colon, no relief is to be expected. Another equally unfortunate kind is when a sort of rectum is rolled up like a bit of catgut. Here all attempts to assist are vain; for though a discharge should be obtained, as the intestine is deficient, evacuations could not be continued.

The means of relief, in the first three of the above classes, are the same. In either of them the operation should be performed without delay or regard to any objections; for, otherwise, death will inevitably follow. The best instrument is a large trocar, such as is employed for tapping in the ascites. The point of the trocar must be kept within the canula until it is fixed against the obstructing part; then pushed forward; and, if you succeed, the meconium will instantly be discharged: this discharge may be left to itself for three or four hours, or until the belly is well emptied. Afterwards pass a finger up the rectum, to discover whether there is any stricture. If a stricture is met with, introduce a probe pointed knife on the back of your finger, and divide it on each side. To finish the cure, let a small candle be introduced Up the gut every two or three hours, or kept there until the anus is quite pervious, and no more aid appears to be required. In two or three weeks the stools will pass properly, and all inconvenience will generally be ended. See Bell's Surgery, vol. ii. p. 275. Edinb. Med. Comment, vol. iv. p. 164. White's Surgery, p. 379.