These form a great reservoir along which the contents are passed very slowly, and probably in a manner different from that in the small intestines. In the cecum and ascending colon so much liquid is absorbed that by the time the residue reaches the transverse colon it has begun to take on the consistence of feces (Roith). Regular antiperistalsis has been observed in cats and other animals; and, as shown by the x-ray in man, it takes but a few moments for a rectal injection to reach the cecum.

The time normally required for the passage from stomach to rectum has been studied under the x-ray by meals mixed with bismuth salts. For the first portion of a bismuth meal to reach the cecum Hertz found the average time to be four and a half hours, and for the last portion nine hours. Satterlee and LeWald, in 27 cases, found two hours the average time for the food to reach the cecum, only one hour being required in 3 cases,

Fig. 2.

Fig. 2. - Chart showing local and central innervation of the small intestine (after Dixon) and the longest time being five hours. In 9 cases it took from four to seven hours for complete emptying of the small intestine. Hertz found that the hepatic flexure is reached in six and a half hours, the splenic flexure in nine hours, the iliac colon in eleven hours, the pelvic colon in twelve hours, and the lower part of the pelvic colon in eighteen hours. At this point is the pelvirectal reservoir in which the contents remain until defecation. Bismuth meal pictures do not, however, tell the rate of a normal mixed meal. In a patient with an ileal artificial anus, Lynch found that a mixed meal appeared in seven hours, while the bismuth meal did not appear for twelve hours.

On arising in the morning or on eating breakfast, as observed by Hertz with the x-ray, peristalsis begins in the colon and carries the feces into the rectum. When the rectum becomes distended, the subject receives subjective sensations of a desire to go to stool. At stool the abdominal muscles are contracted so that more material is forced into the rectum and into the anal canal. This results in the defecation reflex, with relaxation of the anal sphincters, colon peristalsis, and renewed contraction of the abdominal muscles. At stool the whole large intestine from splenic flexure onward is emptied, a relatively long column of feces resulting. In addition, while the act of defecation is taking place, a portion of the contents of the transverse colon may move into the descending colon and pass out. The shape and the size of feces as passed are largely determined by their consistence and by the irritability of the anal canal, and not by strictures high up in the rectum.

According to the above, the stool normally contains the food-products which have reached the splenic flexure. Hence the first portions of a meal eaten nine or ten hours before will normally appear in the stool, while a portion of the residue from that meal will not appear until the next stool. If there is but one stool a day, therefore, it will normally contain material from the food eaten as much as thirty-four hours before. Hence, Hertz concludes that if, after a morning defecation, the residue of food taken at 4 p. m. does not appear in the feces the second morning after, there is constipation. To check off the material of a given meal, it is customary to give a capsule of 5 grains (0.3 gm.) of carmine, or half a dozen lozenges of charcoal, about 30 grains (2 gm.), with the meal. These color the feces from that meal pink or gray-black respectively. (Excellent reference works on the actions of the bowels are: Hertz, "Constipation and Allied Intestinal Disorders," 1909; W. B. Cannon, "The Mechanical Factors of Digestion," 1911.)

Griping or cramp is a condition often produced by cathartics.

It is probably caused by a spasmodic contraction at the site of an irritant, instead of coordinated peristalsis. The work of Hertz suggests that the distention behind the contracted ring may be the cause of the pain.