A clyster, (from Enema 3393 to inject,) enclysma, catlaysma, and lotio. Any liquid medicine injected into the anus. Clysters are usually injected by means of a bladder and pipe, called elusma, fistula, ou/iscos; from whcnce fistula armata, pipe, and bladder: but in many other countries a syringe is always used, by which the liquor is thrown up further into the bowels.

The quantity of liquor used in each clyster will vary according to the age of the patient and intention proposed. For infants, two ounces are sufficient; a child of six years old, from six to eight ounces; a youth of fourteen years, from eight ounces to a pint; and to an adult, from a pint to a pint and half. In general, the bulk should be considerable; for they stimulate from their bulk alone, and a quart of milk and water will often produce the appropriate effect; a circumstance of some utility, when the too anxious friends dread every evacuant. When the more active purgatives are thus combined with increased bulk, they seldom fail.

Clysters seldom reach beyond the sigmoid flexure, or that turn of the colon, on the left side, before its straight direction obtains for it the name of the rectum. They thus operate chiefly by stimulating the lower part of the gut, and evacuate only to the extent which that stimulus reaches. They are of little use, therefore, as evacuants, unless a purgative has been taken, whose effects we wish to hasten. This is often of considerable service where only small doses of cathartics can be retained; for by these means they prove effectual; and frequent solicitations by clysters produce, in such circumstances, the best effects.

In diarrhoeas, and all disorders where the intestines are weak, or whenever the clyster is to be retained, the quantity for an adult should not exceed five or six ounces.

In ardent fevers, and inflammations of the bowels, they answer the end of a fomentation, and should be administered from a pint to a quart. In putrid fevers, this mode of introducing the bark and fixed air into the constitution has been adopted, it has been said, with success. Nourishment may be conveyed by clysters, when, from some complaint of the mouth, throat, or stomach, nothing can be swallowed or retained: many have been thus supported during several weeks. In such cases a quarter of a pint of rich broth is injected, with thirty or forty drops of tinctura opii, every five or six hours, and bark with port wine has been injected in the same way. The effects are not, however, so decidedly beneficial as they have been represented."

Clysters should never be either hot or cold when used; but so warm, that, when inclosed in a bladder, the heat gives only an agreeable sensation to the closed eye lid.

When a clyster is intended only to evacuate, three or four ounces of common salt, or as much soap in a pint and half of water, are sometimes equally effectual with any quantity of the other purging medicines.

When a very powerful stimulus is required in purging clysters, it is usual to mix emetics with them, and of these the vinum antimonii merits, it is said, the preference. But any of the more active purgatives will equally succeed; and there is not a more effectual purgative clyster than three drachms of the pulp of colocynth, boiled for a quarter of an hour in a sufficient quantity of water, to strain off a little more than a pint. To this should be added two ounces of oil, and as much vitri-olated magnesia.

The usual method of injecting clysters is very inadequate, and often ineffectual. An injecting syringe, which holds a pint and half, is the proper instrument; and it is sometimes of advantage to have a lateral pipe, by which it may be supplied without withdrawing. We might thus even fill the colon, and produce many beneficial effects; since a fomentation could be in this way effectually applied to many important parts, when in a state of inflammation, or otherwise diseased. De Haen, by such an instrument, filled the colon of a dog, and in some experiments even conquered the obstruction which its valve offers.

Enema ex amylo. See Amyumi.