Anus

[Lat.] ( Anat. ) The fundament; the lower extremity of the great intestine, named the rectum. Its office is to form an outlet for the fæces. The anus is furnished with muscles which are peculiar to it, viz., the sphincter, which forms a broad circular band of fibres, and keeps it habitually closed, and the levatores ani, which serve to dilate and draw it up to its natural situation, after the expulsion of the feces. It is subject to various diseases, especially piles, ulceration, absce es, excrescences, prolapsus, and imperforation in new-born infants. - The term A. is also applied to a small opening of the 3d ventricle of the brain, which leads into the 4th.