To aid in the surgical description and for the purpose of locating diseases in general as described in this text the following anatomical divisions will be adhered to.

The Anal Canal

The Anal Canal is that part of the intestinal tract below the junction of the true mucous membrane with the skin. It is situated in the middle of the pelvic outlet on a level with an imaginary line drawn between the tuber mischief. The canal measures from two-thirds to one and one-half inches in length, is shorter when the rectum is distended, and extends from the true skin below to the free borders of the semi-lunar valves, or the anew-rectal line above. It lies in a downward and backward direction, making an angle of more than 45° with the horizontal. The outer coverings are composed of a prolongation of the rectal fascia, the internal and external sphincters, and the split elevators an muscles, forming a muscular cylinder which is steadied by the staphylococcal body posterior. The is chi-rectal Fosse are situated on each side: anterior the base of the triangular ligament and the bulb of the urethra in the male, and in the female, the perinea body of the vagina and a mass of fat and muscular tissue.

Posterior, a dense ridge of skin, known as the anal rape, extends from the anus to the coccyx, while in front of the proper the perinea rape is continuous with the rape of the scrotum.

The interior of the canal is lined by a much-cutaneous and mucous layer. The much-cutaneous layer is richly supplied with terminal nerve ends and contains a few glands and blood vessels. The lower portion of the mucous membrane is composed of stratified, squamous epithelium, which gradually undergoes a change to the columnar variety at the lines dentally or anew-rectal line, marking the upper limit of the anal canal. At this point, the mucous membrane presents a orientated appearance due to from five to eight slight elevations above the surface of the mucous membrane which forms an irregular border between the rectum and the anal canal. The area is described by some authors as peculiarly supplied with nerve terminals giving rise to many reflex disturbances.

About one-fourth of an inch below the anew-rectal line, the lower end of the internal sphincter is marked by a poorly defined white line, technique known as Hinton’s, which is almost imperceptible to the naked eye, but is easily discernible by the touch. This line is of importance as marking the junction between the internal and external sphincter muscles.

The External Sphincter Muscle. The anal canal is surrounded by the external sphincter muscle, which is voluntary and situated just beneath the skin at the anal margin, being so adherent to the skin, that care should be exercised against its removal with the skin. It takes its origin from the tip of the coccyx and after encircling the anus is inserted into the perinea body. The muscle is about one-half inch broad, is quite thin, and its fibers are penetrated by a portion of the longitudinal fibers of the rectal wall which separate it into an external and internal portion. These fibers form a plane upon which pus may burrow from a superficial mischief-rectal abscess to the rectum. The muscle is supplied by the fourth sacral and inferior hemorrhoid nerves.

The Internal Sphincter is situated just above the external sphincter muscle and is a flat, involuntary muscle, consisting of simply a number of the circular muscle bands of the rectum grouped together at that point to form a muscle three-fourths to one inch in breadth and one-sixth of an inch in thickness. The internal sphincter muscle is regarded by most surgeons as the most important factor in fecal incontinence, beThe Elevator Agni Muscle is a broad thin muscle which forms the floor of the pelvic cavity. It is attached to the inner sides of the true pelvis as far forward as the symphonists pubis; laterally, along the line of the abjuratory fascia and from the spine of the mischief, posterior, on both sides. It unites with the muscle of the opposite side to form the floor of the pelvis. This muscle supports the viscera and the various structures contained in this cavity.

It is inserted into the walls of the rectum and its fibers pass downward and backward to be inserted into the sides of the coccyx and lower part of the sacrum. Its fibers are interlaced at the lower ends with fibers of the external sphincter muscle which often permits the only weak point in the pelvic floor for the escape of pus from the pelvis-rectal Fosse into the mischief-rectal Fosse. The function of this muscle is to lift the anus and compress the neck of the bladder and urethra. Cripes demonstrates that the elevator an has some voluntary action which is shown by the control of the bowel existing after destruction of the external and internal sphincter muscles.

The Mischief- Coccyges Muscle is described by anatomists as a separate muscle, but is considered by most rectal specialists as simply the posterior fibers of the elevator an muscle.

Fig. 1. The anal canal. A. columns of Morgan, crypts of Morgan or semi-lunar valves; C. dent ate border, surmounted by papillae; D, Hinton’s white line purely an involuntary muscle which becomes useless if the normal muscular action is interfered with by destruction of its nerves or tissue.

The Recto-Coccyges Muscles, which represent two fiat bands of pinstriped muscular fibers, arise from the coccyx ligament near the tip of the coccyx, pass forward, downward, and blend with the longitudinal muscle fibers of the rectum and pelvic fascia surrounding the anus. This muscle is supposed to be a tensor of the pelvic fascia and a detractor of the rectal wall.