of experiment in a manner so satisfactory as by Majendie,* who appears not to have been entirely aware of the advancement made by Mr. Bell in the same path of discovery, as he states that he "had not entertained the slightest idea of what would be the probable result of this experiment." He exposed the posterior half of the spinal marrow in a puppy, and, by proceeding carefully, was enabled to expose the posterior roots of the lumbar and sacral nerves; these were subsequently divided with a pair of fine scissars, without injuring the spinal cord. The limb, when pricked or violently pinched, was, to all appearance, without any sensibility or power of motion; when, to his surprise, the animal began to move it very distinctly. A second and third expe. riment was followed by similar results; and M. Majendie, being assured that the sensibility was destroyed while the power of motion remained, was led to suppose that the posterior roots gave sensation without motion. To prove the converse of this hypothesis, it became necessary to divide the anterior roots, leaving the posterior untouched. This, however, was an experiment more easily planned than executed. After various unsuccessful attempts, M. Majendie found that, by tearing off the dura mater from the spinal marrow, he could display the anterior roots united in bundles, just where they pierce that nembrane, and so divide them. The limb was altogether deprived of the power of motion, yet its sensibility was retained. These experiments were repeated and varied on different animals, and the results, both with respect to the anterior and posterior roots, were confirmed in the most satisfactory manner. Such is the first paper of M. Majendie; a second has been published in the Number of his Journal for October, the principal part of which we subjoin. He then wished to ascertain whether it were possible to divide the anterior or posterior roots of the spinal nerves, without opening the covering of the spinal marrow; for, on exposing this to the air and cold, the nervous power is sensibly diminished. The anatomical disposition of the parts did not render this impossible, for each fasciculus travels for some way in a canal proper to itself before it joins the other. In effect, he found that, with the aid of a blunt-pointed scissars, he could remove the parts sufficiently to lay bare the ganglion of each pair of lumbar nerves; and then the canal which contains the posterior roots could be separated by a small stylet, without much difficulty, and subsequently divided. This manner of conducting the experiment afforded the same results as had previously been observed; but, as the experiment is much more difficult, M. Majendie prefers the method described in his first paper. Being desirous to ascertain whether convulsions would be excited in a member, the nerves of which had been divided, and if they would take place to the same extent as usual when the nerves of sensation were destroyed, he applied the nux vomica, with the following results:-In an animal in which the posterior roots were cut, the muscular contraction was as great as if the origin of the nerves had remained untouched: on the contrary, in an animal in which the nerves of motion were divided, the member which they supplied Journal de Physiologie, Août. remained supple and unaffected at the time when the other muscles of the body were powerfully contracted by the influence of the poison. In pinching or pricking the posterior roots, the animal showed symptoms of pain, but not nearly to the same extent as when the spinal marrow was touched, although slightly, at the place where the roots take their rise. Almost every time that the posterior roots were thus irritated, contractions were excited in the muscles supplied by them: these contractions, however, were infinitely weaker than if the spinal marrow itself were touched. The same trials were made with regard to the anterior roots, and, as might be expected, with opposite results; the contraction being powerful, and even convulsive, while scarcely any symptom of sensation was evinced. The parts were next subjected to the action of galvanism: in the first instance, leaving them in their natural state; and, in the second, dividing the spinal extremity, so as to place it on an isolated body. Contractions were produced by means of either root, but those excited by the anterior were in general much stronger, and more complete, than when the posterior were the media of the electric influence. M. Majendie informs us that he is now occupied in tracing the phenomena of sensation and of motion in the spinal marrow itself; and it is but justice to this industrious experimentalist to state, that he gives the merit of originality to Mr. Charles Bell, limiting his own claims to the performance of the ingenious experiments which we have above detailed.* Within the period allotted to this Essay, a continuation of Mr. Bell's first paper, in the Transactions of the Royal Society, has been published: it relates to the nerves which associate the muscles of the chest, in the actions of breathing, speaking, and expression. He informs us that "The nerves on which the associated actions of respiration depend, and which have been proved to belong to this system by direct experiment and the induction from anatomy, arise very nearly together. Their origins are not in a bundle, or fasciculus, but in a line or series, and form a distinct column of the spinal marrow. Behind the corpus olivare, and anterior to that process which descends from the cerebellum, the corpus restiforme, a convex strip of medullary matter, may be ob served; and this convexity, or fasciculus, or virga, may be traced down the spinal marrow, betwixt the sulci, which give rise to the anterior and posterior roots of the spinal nerves. "This portion of medullary matter is narrow above where the pons Varollii overhangs it. It expands as it descends; opposite to the lower part of the corpus olivare it has reached its utmost convexity, after which it contracts a little, and is continued down the lateral part of the spinal marrow. "From this track of medullary matter on the side of the medulla oblongata arise in succession, from above downwards, the portio dura of the seventh nerve; the glosso-pharyngeus nerve; the nerve of the par vagum; the nervus ad par vagum accessorius; the phrenic, and the external respiratory nerves. * Journal de Physiologie, Août et Octobre. "It is probable that the branches of the intercostal and lumbar nerves, which influence the intercostal muscles and the muscles of the abdomen in the act of respiration, are derived from the continuation of the same cord or slip of medullary matter. Nor will it escape observation, that the nerves called phrenic and external respiratory, though coming out with the cervical nerves, do, in all probability, take their origin from the same portion of the medulla spinalis with the accessory nerve. "The intercostal nerves, by their relations with the medulla oblongata, are equal to the performance of respiration, as it regards the office of the lungs; but they are not adequate to those additional functions which are in a manner imposed upon the respiratory apparatus, when they are brought to combine in other offices." In the usual state of the body, Mr. Bell regards the intercostal muscles as sufficient for the performance of respiration; but, under circumstances which render the breathing more difficult, the diaphragm, the trapezius, the serratus magnus, and the mastoid muscles, are called into action, and it is to these alone that the nerves called respiratory of the chest are distributed. "If we examine the par vagum, the portio dura of the face, the external thoracic, the diaphragmatic, and the spinal accessory nerves, by comparative anatomy, we shall conclude that they are all respiratory nerves, by their accommodating themselves to the form and play of the organs of respiration. In fishes, the respiratory nerve goes out from the back part of the medulla oblongata. When it escapes from the skull, it becomes remarkably enlarged, and then disperses its branches to the bronchiæ and the stomach. But from the same nerve go off branches to the muscles moving the gills and operculum, whilst a division of the nerve is prolonged under the lateral line of the body to the tail. It is said this division sends off no branches, but this is not correct; it gives branches in regular succession to the muscles from the shoulder to the tail. Experiments have been made upon these nerves, but their detail would lead us too far. It is scarcely necessary to add, that there is neither phrenic nor spinal accessory, nor external thoracic nerves, in fishes,-the order of their muscular system not requiring them. In birds, the structure of the wing, and the absence of the inastoid muscle, render the spinal accessory nerve unnecessary; it is wanting for the reason that, in the absence of the diaphragm, there is no phrenic nerve. Quadrupeds have the three respiratory nerves of the trunk; but even in them there are variations in the muscular frame, which illustrate the appropriation of the nerves. The construction of the neck of the camel is like that of birds: there is a succession of short muscles along the side of the neck, and attached to the vertebræ; but there is no long muscle, like the sterno-cleido-mastoideus, contributing to the motion of respiration. There is, accordingly, no spinal accessory nerve in the neck of this animal. “We have a remarkable example of the manner in which these nerves vary in their course of distribution, and yet retain their appropriate functions, in the nerves of the neck of birds. In them, the bill precludes the necessity of the portio dura going forward to the nostrils and lips; the nerve turns backwards, and is given to the neck and throat; and it is particularly worthy of remark, that the action of raising the feathers of the neck, as when the game.cock is facing his opponent, is taken away by the division of this nerve.' These nerves are likewise regarded as organs of expression, and their functions further illustrated from pathology; but our limits will not admit of our entering more minutely into the subject. For an excellent general view of the opinions and experiments of Messrs. Bell and Shaw, we refer our readers to the paper, by the latter gentleman, inserted in our last Number; and to the Medical Intelligencer, No. 36, for a clear and impartial analysis of all that has been published on this subject, with the exception of Mr. Wallace's paper,† and that of Mr. Shaw just alluded to. A full account of Mr. Mayo's experiments and remarks was given in this Journal for November. PATHOLOGY. Some observations occur in the two last Numbers of the Edinburgh Medical and Surgical Journal on the subject of Purpura Hemorrhagica; and, from the dissection of two cases, it appears evident that the petechiæ are not confined to the dermoid system. Indeed, this fact had been ascertained before, and an interesting case is to be found in the Number of this Journal for April, in which appearances presented themselves similar to those about to be described. In both the above cases, purple spots were observed studded over the viscera of the thorax and abdomen; and these were not confined to the serous textures, as the internal surface of the heart, stomach, and bladder, were spotted in one or other of them. In Dr. DUNCAN's case," the inte guments were, perhaps, more livid than usual; the tongue was much thickened; there was gangrene of the velum pendulum palati, the tonsils, and pillars of the fauces; the glottis and epiglottis were inflamed; but the redness did not extend into the larynx. The pleura was marked with petechia, and there was an ecchymosis on the right side of the spine; the lungs were healthy; the heart was beautifully studded with petechiæ, some florid, some deep red, some purple; the colon, mesocolon, and mucous membrane of the stomach and of the bladder, presented the same appearance." It is remarkable that in none of the three dissections alluded to was the brain examined. Dr. Duncan very justly calls in question the propriety of ranging this among the cutaneous diseases,—not only because the hemorrhage is much more important than the spots on the skin, but because dissection shows that they are not confined to this part, but are likewise found internally. He regards the disease as essentially a hemorrhage, for each petechia is, in fact, a little ecchymosis; and the great peculiarity of the affection is, that small bleedings take place at very distant parts of the body, and from different textures. The modes in which he regards it as possible for this disease to arise are," 1. Increased tenuity of the blood, allowing it to escape from the superficial extremities of the minute arteries. 2. Dilatation of the mouths of these arteries, allowing natural blood to *Transactions of the Royal Society, 1822. escape. 3. Tenderness of the coats of the minute vessels giving way, from the ordinary impetus of the blood. 4. Increased impetus of the blood, rupturing healthy vessels. 5. Obstruction in the vessels, causing rupture, with natural impetus, and without increased tenderness. 6. Two or more of these causes may act simultaneously, or successively." It is difficult, as Dr. Duncan remarks, to conceive any other way in which purpura can arise; and yet none of these explanations are easily reconciled to the phenomena of the disease: for it is very questionable whether increased action of the vascular system does generally precede the eruption, and still more difficult to believe that tenderness or softening of the minute vessels should take place simultaneously all over the body. He thinks it more easy to suppose that a sudden relaxation of the mouths of the vessels may take place at the same time, or that the disease proceeds from tenuity of the blood, which, when it has arrived at a certain pitch, escapes through the open mouths of all the vessels of a certain size. These cases have given rise to some judicious remarks from Dr. WHITLOCK NICHOLL, who observes, that, from Dr. Duncan's analysis of the modes in which this affection may occur, it is evident that venesection is warranted only by the fourth cause which he has assigned for the origin of purpura, namely, "increased impetus of the blood," except in those cases where the "obstruction in the vessels" arises from an overloaded state of the circulating system. Should this state be referable to obstruction existing in the viscera, as of the spleen or liver, he conceives purgatives will be particularly useful. There remain the first, second, and third heads of Dr. Duncan's analysis, and for these Dr. Nicholl proposes the oleum terebinthine; two cases successfully treated by this remedy having been published by him in the London Medical Repository for July 1821; and, on the present occasion, a third is added. A languid, pallid child, two years and a half old, was brought to him a few days after she had become covered with purple spots all over the skin and in the mouth. A drachm and a half of the oil of turpentine was given daily, in divided doses, with syrup of senna and water; under which treatment the eruption gradually disappeared between the 1st and 11th of December; and, returning in March again, yielded to a similar mixture, alternated with bark and mineral acid. Some very interesting and important remarks on Partial Paralysis, from the pen of Mr. SHAW, are to be found in the last volume of the Medico-Chirurgical Transactions.+ The object of these is to show that the most common cause of such affections of the face is not in the brain, as has often been supposed, but that it generally depends upon some injury or disease of the portio dura, called by him the respiratory nerve of the face." The first series of cases relates to the effects of inflammation of this nerve, and, among others, the state of a person named Richardson is described. On looking at him, there does not appear Edinburgh Med. and Surg. Journal, October 1822. We did not analyze Mr. SHAW's paper along with the others in the Medico. Chirurgical Transactions, intending to give a general view of the new doctrine regarding the functions of the nerves called "respiratory." The paper by Mr. S. in our last Number has rendered this, for the presen', unnecessary. |