| A SYNOPTICAL TABLE OF POISONS, | |||
|---|---|---|---|
| NEWLY ARRANGED | |||
| According to the different Primary Operations, by which they produce their effects, | |||
| With a view to furnish a General Theorem for the administration of Antidotes. | |||
| CLASS I. | Poisons which act Primarily, through the medium of the Nerves, without being absorbed; or exciting Local Inflammation. | ||
| Order 1. | By which the functions of the Nervous System are suspended, or destroyed. | ||
| (Death by Suffocation from paralysis of the Respiratory muscles.) | |||
| Alcohol. | |||
| Aconite. | |||
| Oil of Tobacco. | |||
| Essential Oil of Almonds.[[220]] | |||
| Camphor.[[220]] | |||
| Opium?[[220]] | |||
| Salts of Lead? | |||
| Croton Tiglium.[[221]] | |||
| Order 2. | By which the heart is rendered insensible to the Stimulus of the Blood. | ||
| (Death by Syncope.) | |||
| Infusion of Tobacco. | |||
| Upas Antiar. | |||
| CLASS II. | Poisons which, by entering the Circulation, act through that medium, with different degrees of energy, on the Heart, Brain, and Alimentary Canal. | ||
| (Death in many forms.) | |||
| Arsenic. | |||
| Emetic Tartar. | |||
| Muriate of Baryta. | |||
| Hellebore. | |||
| Savine. | |||
| Meadow Saffron. | |||
| Squill. | |||
| Opium?[[221]] | |||
| Lettuce. | |||
| Henbane. | |||
| Prussic Acid. | |||
| Deadly Nightshade.[[221]] | |||
| Hemlock. | |||
| Camphor.[[221]] | |||
| Coculus Indicus. | |||
| CLASS III. | Poisons which, through the medium of the Circulation, expend their energies upon the Spinal Marrow, without directly involving the functions of the Brain. | ||
| (Death by Tetanic Convulsions.) | |||
| Nux Vomica—and the whole tribe of Strychnus. | |||
| CLASS IV. | Poisons which produce a direct local action on the Mucous Membrane of the Alimentary Canal. | ||
| (Death by Gangrene.) | |||
| Corrosive Sublimate.[[220]] | |||
| Verdigris. | |||
| Muriate and | |||
| Oxide of Tin. | |||
| Sulphate of Zinc. | |||
| Nitrate of Silver. | |||
| Concentrated Acids. | |||
| Caustic Alkalies. | |||
| Cantharides. | |||
| Bryony. | |||
| Elaterium. | |||
| Euphorbium. | |||
| Colocynth. | |||
| Hedge Hyssop. | |||
| Ranunculi. | |||
| Nitre. | |||
The First Class of our arrangement comprehends such poisons as operate, through the medium of the nerves, upon the organs immediately subservient to life; in their application it is obvious that they cannot require to be introduced into the stomach; they may convey their destructive influence by an application to any part duly supplied with nerves, and whose extremities are exposed to their action. It had been long admitted that a poison might occasion death, by acting on the nerves of the stomach and intestines without being absorbed; but to the experimental labours of Mr. Brodie[[222]] we are principally indebted for our present correct views of the subject. The class admits of two important divisions, into one comprehending those poisons which destroy the functions of the brain, and into another, including those which direct their influence upon the heart. We shall offer a few observations upon the facts which have suggested such a division, and upon the practical advantages which may attend its adoption.
It was observed by Bichât, and the observation has been fully confirmed by Brodie, that the influence of the brain is not directly necessary to the action of the heart; and is immediately necessary to life, only because the muscles of respiration owe their action to its influence.[[223]] For when the functions of the brain are destroyed, even when the head is removed, the heart continues to contract for some time afterwards, and then ceases only in consequence of the suspension of respiration, which is under the direct influence of the brain. Assuming this as a fact, it will appear evident that certain poisons may, by affecting the brain, so paralyse the muscles of respiration as to occasion death by suffocation, and by such a mode of operation I imagine that those substances, arranged in the former division of my first class, prove mortal. Mr. Brodie accordingly found that, by the administration of a large dose of alcohol to a rabbit, the pupils of its eyes became dilated, the extremities convulsed, and the respiration laborious, and that this latter function was gradually performed at longer and longer intervals, and that it at length entirely ceased. Two minutes after the apparent death of the animal, he opened the thorax, and found the heart acting with moderate force and frequency, circulating dark coloured blood; he then introduced a tube into the trachea, and produced artificial respiration by inflating the lungs, and he found that by these means the action of the heart might be kept up to the natural standard, as in an animal from whom the head is removed. The same phenomena resulted from the injection of two drops of the Essential Oil of Bitter Almonds, diffused in half an ounce of water, into the rectum of a cat; and from the application of the empyreumatic oil of Tobacco to the tongue, and rectum of cats and dogs. Now it is obvious that the functions of the brain are immediately disordered by the influence of these poisons on the tongue, stomach, and lower bowels of animals, so instantaneously, that it is impossible absorption should have already taken place.
Although the general proposition seems to be established, that the brain is not immediately necessary to the action of the heart, yet it must not lead us to the conclusion that the heart is therefore incapable of being affected by violent impressions on the nervous system; the fact is quite otherwise, for although the brain may be removed, and the circulation be nevertheless maintained by artificial respiration, yet an injury of another kind inflicted on the brain, may be followed by those immediately fatal consequences which decapitation itself would not produce; thus is a blow on the head commonly followed by syncope, and there are certain poisons that would seem to act in the same manner, such is the Infusion of Tobacco,[[224]] which suspends the action of the heart long before the animal ceases to respire, and kills by producing syncope, although in this latter case it has been questioned whether the spinal marrow may not be primarily affected, which has been shewn by recent experiments to have an intimate relation with the action of the heart. Be this as it may, it is sufficiently obvious, that the second division of the first class is sanctioned by theory, and confirmed by experiment.
We come now to speak of the Second Class,—of those Poisons which enter the circulation, and act through that medium on the heart, brain, and alimentary canal. These organs, however, are affected in very different degrees by different poisons, or even by the same poisons, under different circumstances. Mr. Brodie has shewn that vegetable poison, although when introduced into the alimentary canal affect life, in consequence of the nervous sympathy which subsists between these surfaces and the common sensorium, yet, that the same poisons applied externally to a wound, produce their effects exclusively through the medium of the circulation, being conveyed to the brain only by mixing with the blood in its vessels, and not by being conveyed through the lymphatics, for a ligature upon the great blood-vessels prevents their producing deleterious effects; whereas a ligature upon the thoracic duct, or general canal through which all the absorbents pour their contents into the blood, does not in the least retard or prevent the operation of the poison. There are also several of the mineral poisons which, whether introduced into the stomach, or applied externally to a wound, poison the animal in consequence of being carried into the circulation. It had long been supposed that Arsenic occasioned death by inflaming the stomach; but Mr. Brodie has very satisfactorily shewn that its influence arises from its absorption, and that it must be regarded rather as a vital, than as a chemical agent. In the first place, he has found the inflammation of the stomach, in several cases, so slight, that on a superficial examination it might have been easily overlooked; and, in most of his experiments with Arsenic, death took place in too short a time to be considered as the result of inflammation; and in the next place, in whatever manner the poison is applied, whether externally to a wound, or internally to the membrane of the stomach, the inflammation is confined to the stomach and intestines; and, indeed, it is commonly more violent, and even more immediate, when applied to a wound, than when internally administered; and it also precedes any inflammation of the wound. This important fact was proved by an experiment made by Mr. Hunter and Sir Everard Home, and subsequently by the repeated investigations of Mr. Brodie.
It has been just stated that after a poison has found its way into the circulation, it expends its virulence upon some particular organs. In some cases this is much more striking than in others. The preparations of Baryta, and of Tartarized Antimony, attack the heart, and occasion death by syncope. Arsenic is less definite in its action, it influences both the brain and the heart, but with different degrees of force in different cases, so that it is often difficult to ascertain which of these organs is the first to fail in its functions. Hydro-cyanic Acid is absorbed, and destroys life by its action upon the nervous system, whose energies it would seem to extinguish without any ostensible injury to the respiration and circulation; for in all those animals which were killed by it in the experiments of Orfila, Brodie, and others, the heart was found acting regularly, and circulating dark-coloured blood; and in some cases, this phenomenon was visible for many minutes after the animal was in other respects apparently dead.
Some substances would seem to direct their powers to various parts of the alimentary canal; and the appearance so produced might be mistaken for the effects of the local action of the poison, had they not been clearly proved by experiment to have arisen from an application addressed through the medium of the circulation; thus is inflammation of the primæ viæ induced by the contact of Arsenic with an external surface of the body!
The Third Class of my arrangement includes those poisons which enter the circulation, and, through that medium, expend their influence upon the spinal marrow, without directly involving the functions of the brain. M. Majendie, in the year 1809, submitted to the first class of the French Institute a series of experiments which had conducted him to the extraordinary result above stated. He found that an entire class of vegetables (the bitter Strychnus) possesses this singular property.
The Fourth Class comprehends all those substances which destroy life by a local action upon the alimentary canal, not by any impression upon their nerves, but by simply inducing a fatal lesion in the membranes.
Through one or more of the above modes of operation all poisons may be said to produce their fatal effects. In some cases a poisonous substance will be found to act in several different ways; thus, the Nightshade is evidently absorbed, carried into the circulation, and is enabled, through that medium to act upon the brain; at the same time it exerts a local action upon the stomach, although less violent than that occasioned by the acrid poisons; it moreover would appear, upon some occasions, to act directly through the medium of the nerves, like those substances which have been received in our first class, or else, how shall we explain the fact of the pupil of the eye becoming permanently dilated by the contact of the Belladonna with the tunica conjunctiva? It would appear therefore that this plant unites within itself all the three great modes of action, upon which I have just attempted to establish a physiological arrangement of Poisons. So again, Corrosive Sublimate, although placed in the fourth division, as being a substance which destroys by inflicting local mischief, is nevertheless capable of being absorbed. The embarrassments, however, which might be supposed to arise from this double mode of operation, are of but trifling importance. It is to the primary operation of a poison to which we are to direct our attention, the subsequent effects are less important in as much as they are more capable of being controlled.