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 oxalic acid. It has been already mentioned that concentrated oxalic acid is a corrosive: yet it never kills by destroying the function of the stomach. Man, as well as the lower animals, will live several days or weeks without nutriment. Now this poison has been known to kill a man in ten minutes, and a dog in three minutes only. Neither does it always induce, when swallowed, symptoms of an injury of the stomach; for death is often preceded by tetanus, or apoplexy, or mortal faintness. Nor is the violence of the poisoning proportional to the extent of the local injury: in fact, death is most rapid under circumstances in which the stomach is least injured, namely, when the acid is considerably diluted.

Let us now proceed to enquire, then, in what way the influence of a poison is conveyed from one organ to another.

Here it will at once be perceived that the conveyance can be accomplished in one of two ways only. Either the local impression passes along the nerves to the organ secondarily affected; or the poison enters the bibulous vessels, mingles with the blood, and passes through the medium of the circulation. In the former way poisons are said to act through sympathy, in the latter, through absorption.

1. On the Action of Poisons through Sympathy. In the infancy of toxicology all poisons were believed to act through sympathy. Since Magendie's discoveries on venous absorption in 1809, the favourite doctrine has on the other hand been, that most, if not all, act through the medium of the blood. And a recent theory, combining both views, represents that, although many poisons do enter the blood, the operation even of these nevertheless consists of an impression made on the sentient extremities of the nerves of the blood-vessels and conveyed thence along their filaments to the brain or other organs.

The nerves certainly possess the power of conveying from one organ to another various impressions besides those of the external senses. This is shown by many familiar phenomena; and in reference to the present subject, is aptly illustrated by the remote or sympathetic effects of mere mechanical injury and natural disease of the stomach. Acute inflammation of the stomach generally proves fatal long before death can arise from digestion being stopped; and it is accompaned with constitutional symptoms, neither attributable to injury of that function, nor developed in so marked a degree during inflammation in other organs. These symptoms and the rapid death which succeeds them are vaguely imputed to the general system sympathizing with the affected part; but it is more probable that one organ only is thus, at least in the first instance, acted on sympathetically, namely, the heart. The effects of mechanical injuries are still more in point. Wounds of the stomach may prove fatal before inflammation can begin; rupture from over-distension may cause instant death; and in either case without material hemorrhage.