In relation to the general subject of enemata, enough has been said in the first part of this work. (See vol. i. pp. 66 and 67.) We have here only to consider them in reference to the evacuation of the bowels. Medicines operate upon the same principles, administered in this method, as when taken by the stomach. They produce contraction of the bowels, either by irritating the mucous membrane, stimulating directly the muscular coat, as by distension, or through the medium of absorption, as is asserted of aloes. They are administered with several objects, or to meet several indications.

1. They are given to hasten or facilitate the action of cathartics administered by the mouth. it often happens that these carry down the contents of the upper bowels into the colon, and then seem to lose their power. Under these circumstances, a stimulation applied directly to the rectum, and thence sympathetically propagated to the colon, is attended with the best effects. The bowels are more thoroughly evacuated than they would be by the cathartic or enema alone.

2. The stomach may be so irritable that it will not retain purgative medicine; or it may be in a condition quite incompatible with the introduction of any irritating substance into it, as in acute or chronic gastritis; or the bowels may be in a similar state, contraindicating any direct disturbing influence. Under all these circumstances, should it be desirable to evacuate the contents of the bowels, enemata may be employed.

3. in obstinate constipation, whether from want of irritability, or from spasmodic contraction of the bowels, it may be necessary to have recourse to every possible influence, in order to overcome their inactivity or resistance; and enemata are among the measures which may be employed for this purpose.

4. in mechanical obstruction of the bowels from impacted feces, in-tussusceptio, etc., it is often necessary to bring in the aid of enemata. in case of feculent accumulation, they serve to soften and then break up the impacted mass. Should invagination of the bowel have occurred, they promise even more advantage than purgatives, because they apply the force in the proper direction for thrusting backward the intruding portion of the bowel. When the difficulty is owing to chronic stricture, tumours, etc., they are necessary, in order, by reducing the feculent matter to a semiliquid state, to enable it to pass through the narrowed aperture. in any case, even when the cause is not obvious, good may be hoped for from them, and nothing is to be apprehended, with due caution on the part of the operator.

5. in habitual constipation, dependent on torpor of the rectum and lower colon, which often occurs in old persons, they are preferable to laxatives by the mouth, as they do not equally interfere with the digestive process.

6. in flatulence and tympanites, existing mainly in the large intestines, they are very efficient, because operating more immediately upon the seat of the disorder.