A Treatise on Poisons, in Relation to Medical Jurisprudence, Physiology, and the Practice of Physic

SHALL discuss this subject by considering first the mode in which poisons act, and secondly, the causes by which their action is liable to be modified.

SECTION I.-On the Mode of Action of Poisons.

When we attend to the effects which follow the application of a poison to the body we perceive that they are sometimes confined to the part where it is applied, and at other times extend to distant organs. Hence the action of poisons may be naturally considered as Local and Remote.

The Local effects of poisons are of three kinds. Some decompose chemically or corrode the part to which they are applied. Others, without immediately injuring its organization, inflame or irritate it. Others neither corrode nor irritate, but make a peculiar impression on the sentient extremities of the nerves, unaccompanied by any visible change of structure.

We have examples of local corrosion or chemical decomposition in the effects of the concentrated mineral acids or alkalis on the skin, and in the effects of strong oxalic acid, lunar caustic, or corrosive sublimate on the stomach. In all of these instances the part to which the poison is applied undergoes che

mical changes, and the poison itself often undergoes chemical changes also. Thus oxalic acid dissolves the gelatin of the animal textures; and in the instance of corrosive sublimate, the poison is converted into calomel, which unites with the albumen, fibrin, and other principles of the tissues.

Of local irritation and its various consequences we have many examples, from redness, its slightest, to ulceration and gangrene, its most severe effect. Thus externally, alcohol reddens the skin; cantharides irritates the surface of the true skin and causes vesication; tartar emetic causes deep-seated inflammation of the true skin and a pustular eruption; the juice of manchineel* spreading inflammation of the subcutaneous cellular tissue; arsenic all of these effects, as also death of the part and subsequent sloughing. Internally, alcohol reddens the stomach, as it does the skin, but more permanently; while other substances, such as the diluted mineral acids, nitre, arsenic, cantharides, euphorbium, and the like, may cause all the phenomena of inflammation in the stomach and intestines, namely, extravasation of blood, effusion of lymph, ulcers, gangrene. Many of these irritants, such as arsenic, are in common speech called corrosives; but they have not any power of causing chemical decomposition: If they produce a breach in the texture of an organ, it is merely through the medium of inflammation and its effects.

Of nervous impressions, without any visible organic change, few well authenticated and unequivocal instances are known. Mr Brodie mentions a good example in the effects of monkshood on the lips when chewed: it causes a sense of numbness and tingling in the lips and tongue, lasting for some hours, and quite unconnected with any affection of the general nervous system. Another instance, which was mentioned to me by M. Robiquet of Paris, occurs in the effects of the strong hydrocyanic acid: When its vapour was confined for some time in a glass tube with a finger on each open end, M. Robiquet remarked, that the point of each finger became benumbed and remained so longer than a day. These are unequivocal instances of a purely nervous and local impression on the external surface of the body. The most unequivocal instance I know of a similar impression on internal parts is a fact related by Dr W. Philip * Orfila and Ollivier, Archives Générales de Médecine, x. 360. + Philosophical Transactions, 1811, 186.

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A Treatise on Poisons, in Relation to Medical Jurisprudence, Physiology, and ...