This section is from the book "Materia Medica: Pharmacology: Therapeutics Prescription Writing For Students and Practitioners", by Walter A. Bastedo. Also available from Amazon: Materia Medica: Pharmacology: Therapeutics: Prescription Writing for Students and Practitioners.
A cathartic is a measure designed to promote defecation. Such a remedy may be employed - (1) In cases of constipation; (2) for the removal of irritating or otherwise harmful material from the intestines, as in food-poisoning, intestinal putrefaction, and some forms of diarrhea; (3) for general depletion, as in plethoric or dropsical states, cerebral congestion, or at the onset of the infectious fevers.
Constipation is a condition of insufficient frequency of defecation, or of insufficient quantity regardless of frequency, or of hardness and dryness of the feces. The usual number of stools in a day is one or two, but many people rr intain health though they habitually depart from this rule in a marked degree.
The feces are normally composed of food residue, bacteria, secretions, and products of chemic and bacterial activities in the intestinal canal. In some cases the bacteria form as much as one-third of the dried feces (Strasburger).
The Small Intestines. - The peristaltic wave is the active force in the propulsion onward of the contents of the small intestine. Its stimulus depends on the integrity of Auerbach's plexus, and the peristaltic movement is coordinated and purposeful. It involves contraction above the stimulating object and relaxation below it. The wave, once started, is propelled from muscle-fiber to muscle-fiber, directly or through nerve-fibrils, and the wave-like rather than continuous contraction is insured by a short refractory period of the muscle (Magnus). Under abnormal stimuli, as by irritant cathartics, the normal, slow, worm-like peristaltic movement may become a "peristaltic rush" (Meltzer and Auer), with discharge of practically the whole contents of the small intestine into the cecum in a very short time. It is probable that the site of constipation is rarely in the small intestines, except possibly in the neighborhood of the ileocolic junction.