Much pains has been taken by critics to determine the nature of this hebenon, and the question is broached by Dr. Paris, in his Pharmacologia. But though it is evident that no known poison possesses the properties detailed in the above and subsequent lines of the poet, yet it serves to show that the doctrine of absorption was then, as indeed it had long been, very prevalent. Nor can it be considered as less so at the present day; and we find it admitted, not only by the unscientific, but by a large majority of our profession; and even Orfila, whose opinions are entitled to the greatest respect, admits its very general occurrence. Within the last year, two very ingenious experimenters, Morgan and Addison, have published an essay on the subject, in which they attempt to prove, that even if some absorption of matter does occur, it does not produce its evil effects by its presence in the blood, and its consequent immediate contact with the brain, but by the modification induced in the nervous extremities, and thence dispersed through the whole frame.

That poisons are absorbed, even by the skin, admits, we think, of very complete demonstration, by various experiments, Seguin caused a patient to lie down, and having carefully washed the skin of the abdomen, he placed, on different points, several substances, among which were calomel, gamboge, scammony and emetic tartar; the quantity of each being seventythree grains. After ten hours and a quarter, the several substances were collected, and very accurately weighed. The calomel had lost 1-7 grains; the tartar six grains; the scammony 4th of a grain, and the gamboge very nearly two grains. Here it was seen, that the substances which irritated the skin most, were most freely absorbed. Magendie and Delille stupified a dog with opium, to avoid pain. They then amputated the thigh of the animal, leaving no connexion between it and the body, except by inserting quills into the divided ends of the femoral artery and vein; so that while all nervous and vascular continuity were destroyed, the circulation might still continue. They then inserted a powerful poison into the foot, and

in a few minutes the system evinced its influence. By compressing the vein when the first symptoms appeared, and thus stopping the return of blood from the limb to the heart, the symptoms ceased; and were again renewed, when the pressure was removed from the vein, and the blood returned from the poisoned part. This is a very important experiment; and, like those of Seguin, establishes, beyond all doubt, the fact, that the absorption in question does occur. It does not, however, decide the tissue on which the poison acts after absorption; which is the greatest desideratum. Morgan and Addison object to this experiment, that, as it was made on an animal stupified by opium, it cannot be ascertained whether the result depended on the upas tienté, or the opium, or both. This objection is groundless; because there were symptoms, independent of the opium, which could be interrupted or renewed at pleasure, by controlling the circulation of the limb. They also object, and with good reason, that the poison must necessarily pass over the minute nerves on the internal surface of the vein, before it can reach the brain; and they have proved that a poison may produce its effects by mere contact with the inner surface of a vein, without entering the circulation. Magendie merely proves then, that poisons may be absorbed ; and does not, in the least, change the position of the dispute concerning the necessity of contact between the brain and the deleterious substance. Dr. Barry introduced the upas tienté into the thigh of a small dog, and after the symptoms had commenced, he applied, over the poison, a cupping glass; by which the animal was relieved. Morgan and Addison assert that this does not prove the necessity of absorption; in the first place, because they believe that the matter was sucked out of the wound, and secondly, because the edge of the cup made pressure on the nerves proceeding from the poisoned spot, and might, thus, prevent the extension of the local impression. Drs. Pennock and Rodrigue, of Philadelphia, have separately repeated and varied Barry's experiment; and the latter has shown, that the cupping glass stops the symptoms, even when violent; that on its removal the animal is again affected; but that this second attack may be avoided, by cutting out the poison; which, in some cases, cannot be sucked out by the cup. As then the relief, in some cases, at all events, is not produced by the poison being sucked out, it will follow that it is to the pressure on the surrounding parts that the good effects are to be attributed. Rodrigue has even proved that simple pressure, with an unexhausted cup, has the same influence; and that a VOL. VII-NO. 14.

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tight ligature on the thigh of a rabbit prevented the effects of a poison placed in the knee; the symptoms appearing when the ligature was loosened, and ceasing when it was again drawn tight. So far then, we must consider the experiments undecisive, since the pressure, in all these cases, acted upon both nerves and veins; preventing the motion, not only of the blood, but of the nervous principle.

That poisoning may occur without the introduction of the offending matter into the circulation, is very satisfactorily established, by the two experimenters already quoted. Their first proof is drawn from analogy; and refers to the production of general spasm or tetanus, by an irritation exercised on a few nervous extremities. Very small wounds, especially when occurring in hot climates, and affecting the extremities, are sometimes followed by the most acute irritation of the whole nervous system, exhibited in the production of violent and general convulsions, which commonly resist all the efforts of art, and proceed rapidly to a fatal termination. Here then, are effects analogous to those of poisons, produced by mere nervous irritation, without the formation of any poisonous matter; the same symptoms appearing whether the wound suppurate or not. An experiment, however, which is easily made, proves, beyond all possibility of doubt, that some poisons do destroy life by their influence on the extremities of the nerves, in so short a time, as to preclude the possibility of absorption. Drop an atom of pure and concentrated prussic acid into the eye of a large dog. The animal will make two or three hard inspirations, and fall dead. In this case, the effect on a robust animal is instantaneous; and it proceeds almost as quickly to death. Observe the course which the acid must traverse in an instant of time, to reach the brain; it must follow the veins to the right cavities of the heart; thence it is propelled into the lungs, where it is intimately mixed with many millions of times its weight of blood; thence it returns to the left cavities of the heart, and is dispersed throughout the system; a very minute portion of the drop being spread through the whole of the blood of the brain. In this case, the idea of contact with the brain is preposterous; and, in many other instances, is little less probable.

To show that a poisonous substance could exert its influence by mere contact with those capillary threads of the great sympathetic nerve, which are so abundant on the inner surface of veins, and without entering the circulation, a very decisive experiment was tried. The gentlemen already quoted, introduced into the jugular vein of a dog, an active poison; having previously tied the vein below the point at which the substance was

introduced, so that the circulation of the vein was stopped, and the poison confined to the point of insertion. In less than two minutes the animal fell in convulsions, and in three minutes and a quarter was dead. The death, in this case, occurred in less than one-fifth part of the time required when the poison is inserted into a superficial wound. The experimenters seem half inclined to concede in this case, the absorption of the poison by the lining membrane of the vein; but even allowing this, they insist that as the death was far more speedy in this instance than in all the others in which absorption was pretended to have taken place, so it could not have proceeded from such absorption, but depended upon a deadly impression on the nerves of the vein. It is plain, however, that no absorption could have occurred; because the vein, both above and below the poison, was laid bare; and had no connexion with the small vessels of the surrounding parts. The experiment, therefore, shows, that any deleterious influence exercised on the inner surface of a vein, directly implicates the rest of the nervous system; and we shall have occasion to draw an important practical inference from this fact. Barry imagined that he had established his views of absorption, by including, in a ligature, the whole thigh of an animal, except the sciatic nerve, and then applying a poison below the ligature; in which case no effect was produced. But it is very fairly objected by Morgan and Addison, that although the nerve was not included in the ligature, still, the circulation of the nerve being lost, its power of conveying impressions was diminished, if not destroyed; and that the experiment thus loses its value. It is not a little singular, that Dr. Johnson has considered this very objection as applicable to the experiment of Morgan and Addison, in which they introduced poison into the vein around which a ligature was placed. There is, however, no foundation for this remark; because the ligature was applied below the point on which the poison acted; and did not compress any of those nervous filaments on which the fatal influence was exercised; nor did it interrupt the communication of those nerves with the apparatus of the great sympathetic.

Another series of experiments established by Morgan and Addison, for the purpose of proving that death does not occur from the solution of the poison in the blood, and its application to the brain, is highly ingenious, and, we think, satisfactory. They placed the throats of two dogs together, and connected the right carotid artery of each, with the left of the other; so that the blood from the heart of one, passed into the brain of the other. Now, as the only passage of the blood of one dog

into its own brain, was by the vertebral arteries, and as most of the fluid passed by the large carotid arteries into the brain of the other dog, it would seem that if the blood became poisonous, the most speedy way of destroying one animal would be to apply poison to the other. It was found, however, on inserting a poison into the cellular tissue of one of the dogs, that one alone was affected; the other, which had received into its brain, at least, three-fourths of the supposed poisonous fluid, escaping without the slightest symptom, while the animal to which the poison was applied was dying. Though this experiment seems to decide the dispute very fairly, our authors, as if "to make assurance doubly sure" varied the mode of communication between the two animals. They connected the jugular vein of one dog with that of another, in precisely the same way as the carotid arteries in the preceding instance. The blood of one dog flowed into the heart, and thence to the brain of the other; and, of course, if either of the animals suffered from poison in the blood, provided the poison was applied to the head, it must be the one to which the poison was not applied; because all the deleterious matter taken up by the jugular veins, must be carried directly away from the inoculated animal, and thrown into the circulation of the other dog. On inserting the poison into the face of one of the dogs, it alone was poisoned; and the animal which received the supposed poisonous current of blood into its system, was not affected; thus was the preceding experiment confirmed. The experimenters have, however, taken a more comprehensive view of the inferences to be drawn from this last experiment; which proves one of two important facts. Either the poison was not absorbed at all, and produced its effects entirely by its influence on the nerves of the wound, or it was absorbed, and destroyed by contact with the inner coat of the veins which it first entered; losing its power when diluted by entering the great mass of blood in the veins of the other dog. But as it has been previously shown, that poisons are absorbed, we think with them, that we may safely draw the important inference, that they destroy, always, by their influence on the nerves of the surface to which they are directly applied, and on those which are spread over the inner face of the first venous branches they enter.

Before concluding the statement of those opinions which we have been led to form on the modes in which poison may destroy life, we would bring to view some circumstances which may have an influence in supporting those opinions. It is remarkable, that although prussic acid is so rapidly fatal, when applied to the extreme filaments of the nerves, it may be applied with