On awakening, nausea and vomiting are usual, often a severe and miserable headache, which persists a part of the following day.

Opium is one of the most powerful analgesics known. Pain is relieved, probably through the depressing influence of the drug on the perceptive centers in the brain, although it is possible that the entire sensory apparatus, the peripheral ends of the sensory nerves, the conducting path in the spinal cord, and the receiving cerebral center are more or less influenced by the drug.

The action of opium on the spinal cord is complex, since it contains a number of alkaloids which resemble strychnine as well as morphine, whose action is almost entirely cerebral. In the lower animals and in children there is increased reflex excitability from the action of codeine, narcotine, and thebaine, the last resembling strychnine very closely in its action on the reflex motor mechanism of the cord.

Respiration. - The action of opium on the medullary centers is very pronounced, particularly upon the respiratory center.

In very small doses opium slightly stimulates respiration; in full or large doses it is a strong respiratory depressant, its action being upon the center in the medulla. Death is usually caused by paralysis of respiration, the respirations sinking to 6-8 or even less to the minute, and becoming shallower and shallower. In the late stages of poisoning Cheynes-Stokes respiration usually develops.

Absorption and Elimination. - Opium is rapidly absorbed, and is eliminated chiefly by the gastro-intestinal mucous membrane and very little by the kidneys.

Moderate quantities of the drug are oxidized in the body, though when large doses are administered opium may be found unchanged in the urine. It is also excreted in the bile, in the milk, and to some extent in the sweat, which is largely increased by opium, particularly when the drug is combined with ipecacuanha, as in Dover's powder. The sweat is the only secretion augmented by opium, although the manner in which sudoriparous glands are stimulated is not positively known - whether centrally or peripherally.

All other secretions are diminished by opium.

The reabsorption of opium may be prevented by frequently washing out the stomach and intestines, from which viscera the drug is mainly eliminated.

Metabolism. - The action of opium on metabolism is very marked. It locks it up. Lactic acid occurs in the blood from defective oxidization. It diminishes internal cell-oxidization; by limiting muscular activity it lessens the muscle metabolism; and by diminishing the excursions of the respiratory muscles, limits respiratory oxidation and CO2 formation. Patients may be kept alive a long period of time under the administration of opium, and it plays a very important role in the feeding habits of the Orientals.

Temperature is at first raised, but later lowered when free diaphoresis and muscular quiescence are established.

Eye. - The pupils are minutely contracted by large doses, the modus operandi not being fully understood, though probably the action is due to stimulation of the oculomotor center. The pupil usually dilates just before death.

Untoward Action. - Headache, disturbances of hearing, muscular tremor or temporary paralysis, itching of the skin with or without eruption. In case the latter sympton appears, it is commonly in the form of a small red spot resembling roseola. An erythematous inflammation may affect the mucous membrane of the mouth and throat.

Morphine has produced paresthesia of the sense of taste, as well as spasm of accommodation of the eye and edema of the eyelids. Many other untoward manifestations occur, even under minute doses, in persons having an idiosyncrasy against the drug.

Tolerance. - It is a notable fact that the body may become readily accustomed to morphine, and that a distinct tolerance becomes established. Chronic morphine-takers may use enormous quantities, some as high as 100 grains of morphine a day. Whether there is formed in the body an immune substance, thus permitting of such large dosage is not yet established. The researches on dogs by Faust and others would seem to show the possibility of an antitoxic substance being formed, but the question is still open for further investigation. Faust's work also showed that the power of the body to oxidize morphine increases.

Poisoning. - Small medicinal doses of opium, as is known, tend to produce moderate excitement, a pleasing sense of freedom from care, and in sleep, tranquil, even happy, dreams. Far otherwise it is with toxic doses. Under their influence the entire physiological conditions of the system are perverted. Here the drug exerts its baneful effects, and the mind rapidly succumbs to a power over which it has no control. The period of excitement is fleeting, the predominating desire of the patient being to sleep, and from the dull, lethargic stupor which supervenes he is roused only by vigorous and unremitting treatment. Giddiness portends this mental and physical state. The pulse, though still full, diminishes in frequency; the breathing becomes heavy and labored, and finally stertorous; the heart is now apparently seized with an indefinable oppression, and the pupils are visibly contracted; the skin is moist and warm, and the face suffused or at length of a marked cyanotic hue, cutaneous eruptions being not uncommon. Should relief be not forthcoming, the pulse continues to sink; the drowsiness and subsequent lethargy are followed by a state of true coma; the muscular system is wholly relaxed; the reflexes are obliterated, and death ensues from respiratory failure, the asphyxia being closely accompanied by cessation of the heart's action. The toxic dose ranges from 2 to 10 grs. In the treatment of acute opium-poisoning at least three objects are of paramount necessity: to eliminate the poison, maintain respiration, and prevent failure of circulation. The first of these may be attained by emptying the stomach and evacuating the bowels. Active stimulants and irritating emetics are of great service, the latter being assisted by frequent and copious draughts of warm water in the intervals of vomiting, and the doses being large in order to make an impression upon the insensibility of the stomach. Chemical antagonists, such as tannic acid, permanganate of potassium, should be tried. Physiological antagonists, as caffeine, in hot strong coffee or tea (with tannin), and atropine, are the most efficient. Too much atropine should not be administered. Hot saline infusions are occasionally very helpful in diluting the poison in the blood, Counterirritants, flagellation, shouting in the ear, may rouse the patient from his lethargy. Artificial respiration by Sylvester's method, or by a pump is imperative in the very toxic cases. Awakening the patient is very helpful in aiding respiration.