Enemata, or rectal injections, may be for cathartic, nutritive, or cleansing purposes, or they may be employed to supply liquid to the body, to cause the expulsion of gas, or to carry local remedies to the mucous membrane of rectum and colon.

The cathartic enema may be employed both as a softening agent for feces and as an evacuant. It has the advantage of affecting directly the rectal reservoir and its contents.

(a) The softening agents are water, soapsuds, olive oil, glycerin, and oxgall. Hertz found that hard fecal masses in contact with olive oil were not disintegrated in twelve hours, while in contact with water they disintegrated in four hours. Oxgall, also, he found to have no greater softening power than water. Glycerin increases the penetration of the water. In cases of impacted feces it has been the custom to inject fresh oxgall or a 1 to 3 per cent. solution of extract of oxgall (extractum fellis bovis), or warm olive oil, sometimes with the addition of castor oil. But, as just stated, neither oxgall nor olive oil is as effective as water in softening feces; and it is a fact that castor oil has little evacuant power unless it is saponified, as in the duodenum. (Inouye and ato (1911) report that inspissated oxgall, 15 grains (1 gm.) by mouth, promotes the absorption of fat.) For softening impacted feces, therefore, the best enemata are plain water, normal saline, and soapsuds, with the addition of glycerin, 1/2 ounce (15 c.c.) to 1 pint (500 c.c).

(b) The evacuating enema acts either by constituents capable of irritating the rectum or by the mechanical stimulus of its presence in the rectum. It consists usually of from one pint to two quarts of warm soapsuds, or soapsuds with the addition of glycerin, 1/2 ounce (15 c.c.), or oil of turpentine, 1/2 ounce (15 c.c.).

In the cat, Cannon has observed peristalsis of the small intestine as the result of a rectal injection and antiperistalsis of the colon. In tests with bland nutritive enemata of milk, eggs, starch, and bismuth subnitrate he found that in every instance antiperistaltic waves carried the material to the cecum. Small enemata never passed the ileocecal valve, but large enemata of about the capacity of the large intestine would often pass into the small intestine.

In man, if a quantity of liquid is introduced three or four inches into the rectum, the patient being in the knee-elbow position or on the back, it will not infrequently reach the cecum; but this happens, as a rule, only when the liquid is bland and is administered slowly, so as not to start the defecation reflexes. In some cases, however, even an irritant enema passes quickly to the cecum, and in rare instances has been vomited. In these cases, of course, the enema fails to act as an immediate evacuant.

The evacuant enema is given rapidly, and by a sudden distention of the rectum or by direct irritation of the bowel wall results reflexly in active forward peristalsis, at least of the descending colon, with expulsive contraction of the rectum and relaxation of the anal sphincter.

In the treatment of chronic constipation enemata should not be given over too long periods, for they accustom the bowel to the stimulus of a bulk of material greater than that of the normal feces.

Enemata to induce the expulsion of gas may be of soapsuds made from yellow laundry soap; of soapsuds and turpentine, 1/2 ounce (15 c.c.); of turpentine, 1/2 ounce (15 c.c.), with olive oil, 6 ounces (180 c.c.); of ice water; of infusion of chamomile; or of tincture of asafetida, 4 drams (15 c.c.), or spirit of peppermint, 1 dram (4 c.c.), added to a pint of hot water. They are employed in the tympanites of typhoid fever, pneumonia, post-operative intestinal paralysis, etc.

Nutritive enemata are employed for feeding when it is necessary to spare the stomach. They must be small in bulk, i. e., about 6 or 8 ounces (180-240 c.c.), warmed, and slowly administered so that they will not be expelled. They may be given at six- or eight-hour intervals, and their administration should be accompanied by a daily cleansing enema of normal saline or weak soapsuds. The ingredients of the enema should be made as absorbable as possible. The available foods are dextrose, sugar, sugar of milk, fully peptonized milk, whisky, brandy, and raw eggs. The white of egg peptonized with the milk may be absorbed, but the ingredients of the yolk may not be. Dextrose solutions are absorbable, but in strengths above 5 or 6 per cent. irritate and cause evacuation. Whether the other sugars are inverted and absorbed is a question. Magnus says that cane-sugar is absorbable. The absorption of oils is promoted by emulsification with 3 to 5 per cent. of lecithin (Congdon), and this may apply to egg-yolk. It is possible that the ammo-acids, such as tyrosin, histidin, and arginin, may prove useful for rectal feeding, as they represent the end-products of protein digestion. Short and Bywaters found a decided increase in the urinary nitrogen from the administration of amino-acids by rectum. They recommend milk pancreatinized twenty-four hours, with the addition of 5 per cent. of glucose.

Colon or rectal irrigations of saline solution slowly administered, using both inlet and outlet tubes, are frequently employed to clean out mucus or the products of intestinal putrefaction, to activate the kidneys, or to supply fluid after hemorrhage. The inlet tube may be inserted 6 or 8 inches, and the outlet tube about half as far. The "continuous drip" irrigation, in which a flow of warm saline 20 to 60 drops per minute, is kept up continuously, day and night, was recommended by Murphy for postoperative tympanites and shock. Potassium acetate or sodium bicarbonate may be substituted for the sodium chloride.

The rectum is a favorite channel for the administration of warm normal saline solution to supply liquid to the body after severe hemorrhage.

Rectal suppositories may be of wheat-gluten, soap, glycerin, or plain or medicated cocoa-butter. The evacuant ones act largely as a foreign body, mechanically stimulating the rectum to expel it. Even a stick of ice or an undisintegrated stick of soap will often have the same effect. Glycerin suppositories, made of almost pure glycerin, with a little sodium stearate to give a solid consistence, are much employed. The glycerin acts as an irritant in the anal canal, but not in the rectum (Hertz). Suppositories are especially useful where the feces come down to the rectum, but are retarded in their expulsion by a tight or sensitive sphincter. 10