FISSURE.—The domain of surgery includes few diseases which produce such intense suffering to the patient as does the affection under consideration, and none in which proper treatment is followed by more prompt relief and more certain ultimate success. Fissure, although so simple in extent and character and so readily curable, exercises a most potent influence in undermining the patient's health and strength, the constant pain and irritation to the nervous system being more than the majority of persons can endure. DEFINITION.—We may define a fissure, or irritable ulcer of the rectum, as a superficial breach of the mucous membrane in the anal region, of a highly sensitive nature, giving rise to spasmodic contraction and paroxysmal pain of a peculiar character. According to Bodenhamer,[1] its shape may be linear, oblong, or circular. LOCATION.—Its position is usually just within the verge of the anus, beginning at the muco-cutaneous junction or Hilton's line, and extending upward toward the rectum for a distance seldom exceeding half an inch. It may occupy any portion of the circumference of the anal region, but its usual site is at its posterior or coccygeal side. MULTIPLE CHARACTER.—Although this lesion is usually solitary, we sometimes find it multiple, especially when it is of syphilitic origin. AGE AND SEX AFFECTED.—Anal fissure is a disease of adult life, and is said to be more common among women than among men. Very young children, however, are not exempt, as many reported cases show. The late Dr. D. Hayes Agnew[2] mentions having seen it occur in infants not over two months old. Dr. A. Jacobi[3] is of the opinion that this affection is a more common one than is generally supposed, and believes that many of the fretful children who sleep badly and cry constantly, and often present symptoms simulating those of vesical calculus, suffer from fissure of the anus. He quotes Kjellberg, who at the Dispensary at Stockholm among 9098 children found 128 cases of fissure of the anus, of which number 60 were boys and 68 were girls; the majority were less than one year old, and in 73 cases the age was less than four months. ETIOLOGY.—The explanation of the very intense pain by which this disease is characterized is to be found upon study of the structural arrangement of the termination of the bowel, with especial attention to the nerve-supply of the part. Therefore it will be in order to review at this point the more important anatomical features of the lower portion of the rectum.