of dilatation of the pupil of the eye, and disorder of the mechanism of focussing the eye for various distances, resulting in dimness and confusion of vision. Such are sometimes called mydriatics (μυδριάσις, dimness of sight); they embrace belladonna, henbane, stramonium, cryptopia (one of the alkaloids in opium), and Indian hemp.

All of these substances act on the nervous system, and, although the physiological action of each is characteristic, there are many symptoms common to the whole group; indeed the course of action of all shows three well-defined stages :—(1) there is first a period of apparent exaltation of function ; (2) this is followed by a period of diminution and perversion of functional activity; and (3) there is a time of loss of function, in which there is profound coma and paralysis. This is well illustrated by a description of the symptoms caused by opium. A small dose not unfrequently acts as a stimulant; there is a sense of vigour, a capability of severe exertion, and an endurance of labour without fatigue. A larger dose often exerts a calming influence, with a dreamy state in which images and ideas pass rapidly before the mind without fatigue, and often in disorder and without apparent sequence; time seems to be shortened as one state of consciousness quickly succeeds another, and there is a pleasant feeling of grateful rest. This is succeeded by sleep which, according to the strength of the dose and the idiosyncracy of the person, may be light and dreamy, or like natural profound sleep, or deep and heavy, passing into stupor or coma. From this a person may awaken with a feeling of depression, languor, or wretchedness, often associated with sickness, headache, and vomiting. If a person do not thus awaken, and the dose be large, there is the condition of deep coma. The pupils are strongly contracted, the face usually flushed and often purplish in hue, the skin dry and warm, respiration deep and slow, often with the rattle in the throat called stertorous breathing; the pulse is slow, strong, and compressible under the finger; and there is deep unconsciousness, from which, however, the person may sometimes be aroused by shaking or shouting, and into which he at once relapses when left to himself. This condition is succeeded by one of even deeper prostration. The person cannot be aroused; the pupils may now become somewhat dilated, especially on the approach of death; the countenance has a death-like aspect, and a bluish-white tint; the pulse quickens and becomes smaller, and more and more feeble; and the skin is covered with a cold clammy sweat. The vital functions are reduced to the lowest ebb, and death then occurs from failure of respiration. Such a train of symptoms is called narcotism. These general symptoms are of course largely modified by the amount of the dose. If it be very large, the person may pass very quickly into the deeply comatose stage.

A somewhat different mode of action is illustrated by the physiological effects of belladonna, or of its alkaloid atropine or atropia. A small dose causes dryness of the throat and mouth, dilatation of the pupils, dimness of vision except for distant objects, and often double vision. The pulse becomes quick, rising, in an adult, from 80 to 120 or 160 beats per minute; and there is often a bright red flush over the skin. The intellectual powers are at first acute and strong, but they soon become confused. There is giddiness, confusion of thought, excitement, a peculiar talkative wakeful restiveness, in which the person shows that his mind is occupied by a train of fancies or is haunted by visions and spectres. Often there is violent delirium before sleep comes on. The sleep after a large dose deepens into stupor, with great muscular prostration or paralysis. During all the time the pupils are widely dilated. Death occurs from failure both of the heart’s action and of respiration.

The chief facts regarding the true narcotics are briefly summarized in the accompanying table.

Conium or hemlock (the leaves and the fruit of Conium maculatum') and its alkaloid conia are sometimes erroneously classed as narcotics. These substances act more in the way of depressing· or weakening muscular activity, by influencing the motor nerves» or the nerve-endings in the muscles, and they have no effect on sensory nerves and sensory centres. Neither is aconite a true narcotic (see Aconite).

Hydrate of chloral has since 1872, when it was introduced as a therapeutic agent by Dr Oscar Liebreich of Berlin, come into great favour as an anodyne and narcotic. It is ethylic aldehyde in which 3 atoms of chlorine are substituted for 3 atoms of hydrogen; thus :—

C 2 H 4 O + 6C1 = C 2 HC1 3 O + 3HC1.

Aldehyde. Chlorine. Chloral. Hydrochloric acid.

The formula for the hydrate is C 2 HC1 3 O.2HO 2 . In small doses, say 10 to 20 grains, chloral is a pure hypnotic, and the sleep obtained is quiet and refreshing. In larger doses it is narcotic, abolishing thought and motor power, with profound coma. Respiration is much enfeebled, and the pulse becomes small and weak. The pupils are widely dilated. It is not uniform in its action, so· that occasionally death may occur after a comparatively small dose, even in persons who have been in the habit of taking the medicine. For this reason, the habit of taking chloral without, medical advice, and of taking it frequently, is to be strongly deprecated. An allied substance called croton-chloral hydrate (C 8 H 3 C1 3 O 2 .2HO) has no hypnotic properties, but is of use when applied externally for severe neuralgia of the face, due to affections-of the fifth cranial nerve (tic douloureux).

Narcotics are used in medicine for various purposes. (1) Ta relieve pain. The best one for this purpose is opium, either in thesolid form or as laudanum (tincture of opium). It is most useful in cases of spasmodic pain. (2) To cause sleep. In some cases opium may be useful for this purpose; but it causes disorder of the· digestive functions, and there is the further danger of producing; the “opium habit,” a vice ruinous alike to body and mind. On the whole hydrate of chloral is the best and safest hypnotic, but it is not without its dangers, and it ought not to be taken except under medical advice. (3) To allay irritation. Where there is increased sensibility, with continued, irritating though not severe pain in any part, opium or hyoscyamus may be used with benefit. (4) Ta cause dilatation of pupil. For this purpose, solutions of atropine are in constant use by ophthalmic surgeons. A few drops of solution of atropine, or a soluble disk containing atropine, introduced into» the eye, cause dilatation of the pupil and diminished tension in the eyeball, at the same time soothing pain. (5) To arrest secretion. For this purpose opium, or belladonna, and atropine are especially useful. Small doses of atropine are given to arrest secretion in cases of profuse salivation, and extract of belladonna applied to the skin is used for stopping the secretion of milk from the mammary gland. (J. G. Μ.)