As you look inside the incomplete model of the rectum, or rather sleeve, you observe circular muscular bands or fibres which it is necessary to cover with soft spongy or fatty substance in whose meshes are nerves, blood-vessels, etc. This is called the areolar layer or coat. One more layer or coat upon this--the mucous coat--completes the structure. This latter possesses the power of accommodating itself to the distention and contraction of the muscular tube. The mucous membrane is thrown into folds and columns which serve as valves to inhibit the undue descent of the feces, thus assisting the mucous membrane in performing its office. The length of the rectum varies in different persons, six inches is the average length. It is divided into two parts. The upper part is a little more than three inches long; beginning in front of the third sacral vertebra and extending down to the end or tip of the coccyx. In shape this part conforms to the curve of the sacrum and the coccyx, to which it is attached behind. The lower part of the rectum is a little shorter than the upper part, and begins at the tip of the coccyx and extends down with the same curve as the upper part, terminating at the upper portion of the anal canal. Returning to the sleeve again; the portion of it from the shoulder to the elbow illustrates the upper part of the rectum when partially covered with a serous coat on the side opposite the bore (the outside). From the elbow to the wrist-band illustrates the lower part of the rectum, when covered on the outside with an areolar coat. The wrist-band of the sleeve will represent the anal tube if drawn into a pucker and turned slightly backward from the direction of the sleeve of which it is a continuation. The muscular fibres described above likewise enter into the formation of the anal canal or orifice. This orifice is closed by two strong muscles that lie close together and are called internal and external sphincters, which are abundantly supplied with nerves and blood-vessels whose branches extend to the neighboring organs. Nine persons in every ten have more or less chronic inflammation of the mucous membrane of the anus and rectum. In time the areolar and muscular coats become invaded by the morbid process, and this increases the irritability of the tissues of the organ. The change from the normal functions of the anal membranes is slow, and the symptoms are not well marked and are consequently ignored for years owing to inexpertness in detecting an invading serious disease, until the time comes when the suffering can no longer be tolerated by the victim of the neglect.