Active Ingredients. - It is now pretty certain that the poisonous action of belladonna leaves and root is dependent entirely upon the presence of the alkaloid atropia (C17H13NO3), which forms silky, glistening crystals, in bundles of rods and needles (four-sided prisms), heavier than water, odorless, and with a very unpleasant bitter taste that lingers on the tongue. It has an alkaline reaction, and requires 300 parts of cold water, 58 parts of boiling water, 3 parts of chloroform, 40 of benzole, or 30 of ether, to dissolve it. Rectified spirit dissolves it completely, and amylic alcohol almost with equal facility. Its solution rotates the plane of polarization feebly to the left. Atropia is supposed to be identical with daturia, the active principle of stramonium, and probably of other species of datura; only, according to Schroff, daturia is much the more energetic of the two alkaloids. (There is a second alkaloid belladonnine, discovered by Hubschmann in 1858, about which very little is known.)

Something more, however, must be said respecting the active properties of the juice of the ripe fruit. There are reasons for thinking that this juice acts upon the nervous centres as a pure narcotic, and is devoid of the acrid properties of the preparations which are made from the leaves and the root.

In its effects upon the organs of deglutition the poison of belladonna berries seems to claim for itself a certain analogy with that of hydrophobia. All the phenomena are curious, and demand that further experiments should be made with the fruit (as distinct from the leaves and root), with the view to determine the therapeutic value of the former. The fruit, as might perhaps be expected, seems to promise a soothing narcotic medicine, the action of which would be unaccompanied (in general) by results of an irritative nature.

Physiological Action. - Belladonna is both locally and generally an "acro-narcotic," i. e., it is capable of producing both narcotic and irritant effects. Scarcely a subject in the whole range of drug-action has been more elaborately discussed than the poisonous effects of belladonna. It will be well first to describe the more immediately obvious phenomena, as to many of which there cannot be dispute.

Like all the mydriatic solanaceae, i. e., those which characteristically dilate the pupil, belladonna produces a number of effects which group themselves around this well-known symptom, and seem to be inseparably connected with it. Mydriasis may indeed be produced alone by acting locally upon the eye with atropia, etc.; but when it arises as an effect of the internal use of belladonna or atropia, it marks the commencement of a very definite group of poisonous phenomena: dryness and heat of the fauces and pharynx, headache, flushing of face, dimness of vision, or actual amblyopia, and (if the poisoning be carried far enough) delirium, which is often of a noisy character, with bursts of laughter, but, at any rate, always busy, and usually attended by spectral hallucinations.

It is not to be supposed that all these symptoms necessarily occur when dilatation of the pupil is produced by internal doses of belladonna; but mydriasis, caused in that way, is always a sign that the other symptoms named are at hand, and would at once follow any considerable increase of the dose.

Among the phenomena of this stage of belladonna-poisoning is an appearance about which there has been considerable dispute, viz., scarlatinalike redness of the skin. That a more or less diffused erythematous blush upon the skin has frequently been noticed, is admitted by nearly all observers; but great difference of opinion has existed as to the proportion of cases in which it occurs, and also as to its persistence, and the extent to which it may spread. Dr. John Harley,1 for example, says that "generally it is nothing more than a mere temporary blush; but in rare cases, and in persons who are liable to vascular irritation of the skin, the redness remains, and its disappearance is attended by slight roughness and desquamation." He himself mentions two cases, in one of which the patient was "scarlet from head to foot;" and in the other, after the fourth dose of the drug, there was a "scarlatinous tint of skin." Meuriot says that there is a contrast between the cutaneous and the mucous phenomena; the mucous membranes, ten minutes after a subcutaneous injection of atropia, are red, injected, and dry, while the skin ispale and dry, like parchment; sometimes, however, the skin, soon afterward, becomes covered with erythematous redness, and is thus uniform with the mucous membranes. He says that the redness is most frequently seen upon the face and trunk, and does not spread to the limbs.

1 Old Vegetable Neurotics, p. 223, London, 1867.

Many cases are reported in the English journals, and many more in the American ones. Dr. Sinclair's case, in particular, in the Boston Medical Journal, is very curious, the rash described by him being remarkably like scarlatina, and appearing to correspond with three instances in which I have myself seen a bright and livid eruption ensue upon the continued use of the tincture. A similar result followed in a case of the accidental poisoning of a child, three years and eight months old, which came before Mr. Holthouse. The dose so unfortunately administered was about half a grain of pure atropia. The child soon became strangely irritable and excited, though unconscious; the face was maniacally distorted; the pupils were widely dilated and immovable; the lids of the eyes were open, and not affected by passing the fingers before them; the pulse was 170, and somewhat feeble; the skin was pungently hot and dry, and "covered," says the historian of the case, "with a scarlatina-like rash." To these examples I may add the testimony of Dr. Garrod, who says that "belladonna produces redness of the skin."

For my own part, I am convinced that the scarlatina-like rash of belladonna-poisoning is far from being an accidental or rare occurrence. I believe it often occurs, and may occur in any case if the poisonous action of the drug be carried far enough. It is no doubt due to capillary congestion, and this congestion may equally invade the skin and the mucous membranes. The dryness of mucous membranes, and the arrest of secretion from various glands, are portions of the same effect. It is chiefly in actually fatal cases that the full development of this symptom is observed. The dilatation of the vessels which causes it is by some authors1 considered to be a direct paralytic effect of the agent; by others2 it is supposed to be paralysis following on a primary contraction.