These are drugs employed to induce vomiting. To produce emesis requires the coordination of several mechanisms, the following actions being necessary: viz., closure of the pylorus, opening of the cardia, setting or contraction of the diaphragm, and contraction of the abdominal muscles. If the pylorus remains open, the result is "retching." The coordination is presided over by the vomiting center situated in the medulla oblongata. This center is highly sensitive to certain sensory impulses from the stomach, and is also capable of being directly stimulated by certain substances in the circulating blood. The emetic measures in common use may be divided into the local or reflex emetics and the central emetics.

1. The reflex emetics act by irritating the throat or stomach, and are: tickling the throat with a feather, or sticking the finger down the throat, or swallowing one of the following: a large draft of lukewarm water; alum, 30 grains (2 gm.); copper sulphate, 10 grains (1.7 gm.); zinc sulphate, 15 grains (1 gm.); ipecac, 15 grains (1 gm.); tartar emetic, 2 grains (0.13 gm.); yellow sulphate of mercury or turpeth mineral, 2 grains (0.13 gm.); mustard, one tablespoonful (about 10 gm.). The drugs mentioned are all local irritants and systemic poisons, and may do great harm if vomiting fails to come on; hence the dose should not be repeated. (See Ipecac.)

2. The only central emetic in common use is apomorphine hydrochloride, apomorphine being an alkaloid derived from morphine by dehydration. It is soluble in 40 parts of water or alcohol, deteriorates and turns green on exposure to light and air, and is considered unfit for use if on being shaken with a little water it imparts at once an emerald-green tint. The emetic dose by hypodermatic is 1/10 grain (0.006 gm.), and the expectorant dose is 1/30 grain (0.002 gm.).

Quite quickly after a hypodermatic injection of apomorphine nausea comes on, and then, in about five minutes, copious vomiting. The drug is not at all excreted into the stomach, and it acts upon the center directly. Smaller doses are expectorant, increasing and fluidifying the bronchial mucus, probably by a nauseant action. Small doses are said to have a mild, morphinelike effect in promoting sleep; but in the author's tests on 16

• patients for several successive nights, though 1/20 grain (0.003 gm.) proved hypnotic, every patient was nauseated.

Therapeutics Of Emetics

1. To empty the stomach - as in acute indigestion, alcoholism, the ingestion of poisons, etc.

2. To remove an obstruction from the esophagus or respiratory passages.

3. To loosen a ball-valve gall-stone in the biliary passages (nature's way).

4. To relieve spasm or marked congestion in the respiratory passages, as in croup or severe asthma.