tary motion, as has been supposed to be the case by Mr. Brodie in his experiment, we should be happy to receive from the advocates of that gentleman's theory a satisfactory explanation of the result of the experiment just related.

"If, on the other hand, the impression of the poison be carried to the brain by other organs, we, for the present, leave the advocates of venous absorption and infiltration to account for its instantaneous effect upon the system when applied to the mouth." 26.

Mr. Brodie was of opinion, that a poison may act on the brain by entering the circulation through the divided veins of a wounded surface. Having tied the thoracic duct of a rabbit, he innoculated its leg with ticunas, and the poison proved fatal in the usual time; and he therefore concluded the action could not have been through the absorbent vessels. He also maintains that a poison must enter the substance of the brain through the circulation of the blood. In proof of this opinion, he tied a tape half an inch wide round the thigh of the rabbit, having excluded the sciatic nerve; the leg was then poisoned with ticunas; no sensible effect was produced at the end of half an hour, the ligature was then removed, and in twenty minutes the animal was found motionless and insensible. To disprove this opinion the following experiment was made.

"Four drops of Prussic acid were applied to the wounded foot of a full-grown rabbit, by which death was produced in two minutes and a half.

"In another rabbit of the same age a ligature was tied round the leg, to the careful exclusion of the sciatic nerve; six drops of the same poison were then applied to a wound in the foot of the strangulated limb, and without producing the slightest sensible effect.

"Mr. Brodie is satisfied that the poison of Prussic acid acts upon the brain by the medium of nervous communication; it is manifest, however, from the foregoing experiment, that, according to the view which he has taken of the subject, the same argument by which the theory of venous absorption is supported in reference to the poison of woorara, holds equally good in this case as applied to the poison of Prussic acid.

"Either, therefore (according to Mr. Brodie's train of reasoning,) we have a direct proof that Prussic acid does not act upon the brain by the medium of the nerves, or we must consider this theory respecting the venous absorption of other poisons to be entirely unsupported by the result of the experiment upon which that theory was principally founded; for, according to the position which Mr. Brodie has taken, the application of Prussic acid to the strangulated limb ought to have produced its usual effect upon the system; whilst the division of the spinal marrow, according to his views of the subject, ought to have precluded the possibility of any nervous communication between the brain and any part of the lower extremity to which that poison had been applied; yet, in both cases, we find that such a supposition is directly opposed to the evidence of fact.

"Whether, therefore, the poison of woorara affects the system through the medium of nerves, or whether it be carried to the brain by the circulation, is a question which cannot be satisfactorily settled by the experiment which Mr. Brodie has instituted, for the purpose of settling that disputed point, since the explanation he has given of their results is directly contradicted by the other experiments mentioned." 33.

Mr. Brodie's theory of the absorption of a poison through a divided vein is also opposed, and decided to be "physically impossible. We must here insert the reasons assigned in the words of the authors, as we find it impos

sible to condense, or rather to comprehend the ambiguity of the two following sentences. We are not disposed to criticise severely the style of modern writers, but we cannot but animadvert on the extraordinary length of most of the sentences of the present work, which often renders the meaning obscure, and confuses the mind with the multiplicity of opposite facts and opinions which are included in a single period. We offer the subsequent examples in justification of this remark.

"When a vein is divided, it is well known, that unless some branch be interposed between the truncated extremity and the next valve in its course towards the heart, unless the current of blood be driven through the cut extremity of the tube by collatera! branches, we find that the sides of the vessel as far as the next valvular interruption will collapse and remain inactive supposing the poison, then, to enter this flaccid tube, it is completely prevented from mixing with the circulating blood which fills the vessel above the valve by the pressure made by that circulating blood upon the opposite side of the valve, and, consequently, under such circumstances, unless it can be proved that a poison has the property of propelling itself, it requires no argument to prove that the substance, instead of passing into the circulation, will remain stationary in that part of the vessel through which no circulation is carried on. If, on the other hand, circulation be carried on by collateral branches through that part of the tube which lies between the nearest valve and the mouth of the divided vein, the effect will be still more unfavourable to Mr. Brodie's hypothesis; for the circulation in that part of the vessel will be reversed, and, consequently, instead of being carried towards the heart, the poison will be washed out of the wound: in either case, therefore, it seems highly improbable that the poison can pass through the circulation to the brain by the medium of a divided vein." 34.

Again we find it impossible to condense the concluding censure on Mr. B.

"With regard to the general theory of venous absorption, as supported by Mr. Brodie's experiment of applying a ligature to a limb which has been poisoned, we have to observe, that the experiment will admit of a different explanation from that which he has furnished us; for since it is proved that the nerves of sensation and volition are not necessarily concerned in carrying to the brain the impression of a certain poison, which he admits must affect the system by nervous communication with the sensorium; since it is therefore obvious that other nerves, performing different functions, must be concerned in the operation of that poison upon the brain; since we have proved that a ligature placed around the limb, to the exclusion of the sciatic nerve, in the manner above stated, produces the double effect of paralysing the nerves upon which one poison operates, as well as of stopping the circulation through the part, it may be fairly inferred, that if the other poison should happen to act upon the brain by the medium of the same set of nerves, the operation of that poison during the period of strangulation would be suspended from a similar cause, and that, consequently this experiment relative to the absorption of woorara is quite inconclusive as supporting the truth of either theory." 36.

Having disposed of Mr. B.'s opinions, our authors proceed to examine those of M. Magendie, the substance of which is, that the admixture of all poisons with the blood in the poisoned part is absolutely necessary to their operation on the body; and this deduction was made from the following experiment, which our authors " oppose in the strongest possible manner. A dog was stupified with opium, and the femoral artery and vein were divided, but re-united by pieces of quill which were secured in the truncated vessels, the limb was amputated, all nervous connexion with the body

of course destroyed, but the circulation was interrupted. The poison of upas was applied to a wound in the severed limb, and produced its deleterious effects in the usual time. Pressure was made occasionally on the vein, when the symptoms of poisoning ceased, but returned after the removal of the pressure. This experiment appeared perfectly conclusive as to the absolute necessity of venous absorption, as the medium of conveying the action of the poison to the brain. The substance of our author's objection to this experiment is, that if a dog be stupified by opium, it is impossible to determine, if upas be applied, whether the animal shall have been destroyed by the one or the other, or by the combined action of the two. Again it is maintained, that the poison must have acted on the inner surface of the veins and arteries before it could reach the brain; or, in other words, on the capillaries or nerves of such surface. It is also doubtful, whether the brain, or the nerves of the vein to which the poison has been applied, receive the first impression. We hope we have been correct in stating the meaning of the passages, which we have condensed-on the whole, the experiment only proves the entrance of the poison into the vein; nor is it to be inferred, that such application of a poison is absolutely necessary to its operation. Our authors conclude in these words:

"We contend, then, that M. Magendie has left the question relative to the necessity for venous absorption and cerebral contact, as connected with the operation of poisonous agents, in precisely the same state as he found it." 50.

The opinions of Dr. Barry are next noticed, and the following experiment commented on. Dr. B. introduced four grains of upas tieuté into a wound on the thigh of a small dog: and applied a cupping-glass and piston to a similar wound, but unpoisoned, in the opposite thigh. Symptoms of poisoning took place in eight minutes. The cupping-glass was then removed to the poisoned wound, a vacuum established, and instantly the symptoms were alleviated. "The animal was truly recalled to life, but from time to time suffered slight attacks of tetanus. After a quarter of an hour the glass was removed, and the animal appeared restored to health. Our authors observe in italics, "the animal was found dead some hours afterwards;" and they cannot comprehend the reason of applying the cuppingglass to the simple wound in the unpoisoned limb. Dr. Barry concluded from this and many other experiments, that the circulation through the extreme branches of veins is kept up by atmospherical pressure upon the surface of the body, and that venous absorption is necessary as a means of communication between a poisoned surface and the brain. To the last conclusion our authors object in these words :

"It will, we think, be admitted by every one, that the soft structures of the surface of the body, which are covered by an exhausted cupping-glass, must necessarily, from the pressure of the edges of that glass, be deprived for a time of all connection, either nervous or vascular, with the surrounding parts. That the nerves must be partially or altogether paralysed by compression of their trunks, and that, from the same cause, all circulation through the veins and arteries situated within the area of the glass must cease: this, however, is not the only change which is produced in a part by the mode in which Dr. Barry has, in his experiments, removed from it the pressure of the atmosphere; for, not contented with merely stopping the circulation, we are informed that the rarification of the air within the glass was still further increased by means of a

small air-pump attached to it, so that the fluids contained in the divided extremities of the vessels were forced into the vacuum, and with these fluids, of course, either a part or the whole of the poison which had been introduced.

"In such a condition of parts, it will be manifest that the compression on the one hand, and the removal of the poison from the wound on the other, will explain in a very satisfactory manner the result of the experiment, as well to the advocate for nervous communication, as to the supporter of the theory of venous absorption. For if the extreme branches of the nerves of a wounded part be paralysed by the pressure of a cuppingglass, of course no sympathy can be established between those nerves and the brain. Or, if the poison be entirely removed from its contact with the nerves by the formation of a vacuum over the wound, we may reasonably suppose that the cause of irritation being no longer in operation, the effect will be no longer apparent; and, consequently, whether the impression made upon the system be the effect of the actual contact of that poison with the brain by the medium of venous absorption, or whether it be produced by nervous sympathy, we may in either case expect from Dr. Barry's experiments precisely the same result as he has described to us." 57.

There is a good deal of force in the explanation offered by our authors on the effect of the cupping-glass in the prevention of the action of poisons; but we cannot admit that the confirmation of that fact, or rather the revival of the remedy, is not something novel in the treatment of poisoned wounds ---no matter how the action of the poison is prevented, whether it be by the cessation of the functions of the lymphatics, veins, or nerves of the injured part; the knowledge of the fact is worth all the theories that have ever been offered on the subject. If the remedy prove equally efficacious in hydrophobia as it has in the numerous instances in which animals have been poisoned by venomous reptiles, and of this there is the strongest probability, we cannot help thinking, that Dr. Barry has added something new, and added more real and solid practical information on the treatment of poisoned wounds, than all the writers on toxicology collectively. We by no means assent to all that gentleman's theories; but we fully agree with our Northern contemporary that he is entitled to a very high rank among the ablest physiologists of the present day."* With respect to the opinions of Mayo and others it is said they contain nothing but the restatement of those just adverted to, and therefore it is unnecessary to notice them separately; and thus conclude the preliminary observations on the opinions of former toxicological writers. We now arrive at the second part of the work, which is on the opinions of the authors upon the subject of poisons. Here we deem it right to insert their own language.

"Hitherto we have refrained from declaring any decided opinion whatever as to the modus operandi of poisonous agents on the living body; but having assumed it to be unphilosophical to admit a two-fold operation-to admit that such agents may at one time act upon the general system, through the medium of the sentient extremities of nerves, and at another time by the direct application of the poison to the brain, through the medium of the blood; and having attempted to show the fallacy of those experiments upon which the notion of a two-fold operation of poisons has been founded, we must now venture to acknowledge an attempt to establish the truth of a theory, which we conceive to be supported as well by the experiments of our predecessors, as by those which we have ourselves instituted upon the lower classes of living animals." 60.

*Edinburgh Medical and Surgical Journal, 1827, v. 27.
7

VOL. XI. No. 21.

"In endeavouring to establish the truth of this our theory respecting the modus operandi of all poisonous agents, we cannot be insensible to the powerful array of authority which is opposed to us, nor to the influence which that authority has probably exerted upon the minds of all our readers; we feel, therefore, that we have to contend with the prejudices as well as with the arguments of our opponents.

"Brodie, Magendie, and Barry, all appear to be quite satisfied, that in many instances the venous absorption and direct application of a poison to the brain are absolutely necessary to its operation upon the general system; although they are compelled to admit that some poisons act at once through the sentient extremities of nerves. Dr. Barry, however, has particularly laboured to show in how short a time a poison may reach the heart through the medium of venous absorption; a circumstance calculated, if not really intended, to cast a shade of doubt upon the operation of poisons through the nerves in any case."

61.

We have already given the theory of Dr. Addison and Mr. Morgan, namely, that, "all poisons act on the system through the medium of nerves only." They are surprised that former physiologists should not have admitted this theory. They had seen it exemplified in the effect of opium on a pained part, of belladonna on the iris, and in certain phenomena which take place in disease. Thus

"A person receives a slight lacerated wound, a burn, a puncture from a spicula of wood, or a rusty nail; the irritating cause being removed from the part, all shall appear to be going on well, when suddenly symptoms of tetanus supervene, and proceed to the destruction of life: here we have, then, the mere irritation of the nerves of a small portion of the body, so deranging and involving the entire nervous system, as to give rise to one of the most formidable of all diseases, and this, so far as we know, without the slightest evidence of any absorption of morbid matter into the current of the circulation, and with just as little evidence of any thing noxious being directly applied to the brain. If, then, mere irritation, mechanical or otherwise, prove sufficient to derange the whole nervous system in this instance, where, we would ask, is the difficulty of conceiving that morbid irritation, and consequent general derangement, in the system, should result from the application of a poison, altogether independently of any absorption whatever?" 65.

These are strong facts in support of the proposed theory. Again we are reminded how many poisons act too suddenly for the medium of absorption. It is said, that the exclusion of the sciatic nerve in a limb included in a tight ligature as already described, rendered that nerve incapable of performing its functions in the absence of all circulation. This is a strong objection, but one that equally applies to the experiments of our authors. Of this hereafter.

In confirmation of our authors' deductions the following experiments were instituted.

"To prove the extreme susceptibility of the inner coat of a vein, when exposed to the action of a poison, the following experiments were made:

"The jugular vein of a full-grown dog (in size about that of a common harrier) was laid bare to the extent of about two inches; the circulation through the denuded vessel was then completely stopped by the application of two temporary ligatures, one of which was tied round the upper, and the other round the lower, part of the exposed vein; the vessel was then divided between the two ligatures, and the truncated extremities reconnec ted by means of a short brass cylinder or tube, within which was placed a portion of woorara, of the size of a grain of canary seed. In this way the continuity of the canal between the