The complications of arachnitis are-1. With venous hyperemia of the brain. This is usually seen in drunkards, and leads to a mixed form, in which there is neither an exclusively serous nor puriform exudation, but a combination of the two. If, however, the inflammation thus complicated be peracute, that dangerous form of disease is developed, known as apoplexia serosa. A second complication of arachnitis is with hemorrhagic apoplexy, or, in other words, an extravasation of blood into the substance, or on the surface of the brain. In this case, the symptoms of irritation are repressed by the pressure on the brain, and are only developed when the cause of that pressure is removed. A third complication of arachnitis is congestion of the brain. In this the symptoms vary according to the degree of congestion, and the case is most intense; they are analogous to those of arachnitis complicated with serous apoplexy. These general views are applicable also to spinal arachnitis.

The physiological inferences deducible from these cases of arachnitis are various. Firstly, it is shown that the symptoms of pressure on the brain are not urgent in proportion to the amount of extravasated blood or effused fluid, but have a relation to the rapidity or suddenness with which it occurs. This is a general principle, applicable to all agents injuriously acting on the brain, as moral impressions, &c. Secondly, there is a greater loss of consciousness when the inflammation and its product are situate at the base of the brain than when on the convex or lateral surfaces. It is thus also with cerebral hemorrhages; hemorrhage at the base induces the most profound and incurable coma; hemorrhage into or near the ventricles induces a less profound and more curable coma; the coma from hemorrhage on the periphery is the lightest and the most manageable of all. This general fact is capable of a satisfactory solution, if we adopt the doctrines of reflex cerebral action; and, so far from being opposed to the general opinion, that the mental acts originate in the hemispheres, may be made to harmonize with it. The incident excitor action, which excites the changes in the hemispheres necessary to mental acts, is cut off in its course from the periphery to the centre by the pressure on the conducting fibrils as they pass up from the cord along the base of the brain. A pressure here, indeed, induces a state of the hemispheres analogous to that in sleep; the stimulus from without is stopped. Now, when there is pressure from effusion on the hemispheres, it is only a counter-pressure that is exercised on the base of the brain; and so soon as this is alleviated, the channel of incident excitor impressions is again opened, and pressure is now only exercised on the upper convolutions, a considerable portion of which we know may be injured, and even removed, without any impairment of consciousness whatever. Coma, then, results rather from interruption of function, consequent on an interruption of the flow of the natural stimulus to the brain from the periphery, than on a derangement of structure; it is a result of pressure on the conducting media, rather than on the acting fibres. The same views will of course explain those phenomena (as irregular action of the heart, of the respiratory mechanism, &c.) which are dependent on an obstruction of the cerebral stimulus, in whatever that may consist; while the pressure on the conducting structures at the base interrupts the course of the incident excitor stimulus to the brain, it cuts off the supply of reflex cerebral stimulus to parts below. There is

XLIV.-XXII.

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some consideration due, however, to the fact, that inflammations at the base of the brain are usually the most intense, and the extravasations the greatest, and consequently that the pressure under these circumstances will be greatest. But this circumstance is opposed to the well-known tolerance of injury which the hemispheres exhibit, so that, after all, the inference must be, that the greater the effusion, the greater the pressure on the conducting strands at the base of the brain.

To give the results more in detail. If there be apoplexy at the base of the brain, there is profound and persistent coma, paralysis of all the limbs, paraplegia, and generally a fatal termination. If there be inflammation at the base of the brain, violent spasms, namely, opisthotonos and trismus, followed by deep coma. If there be structural disease at the base, sensorial disturbance, great tendency to vertigo and syncope, titubation, &c.

At the

Paralysis of the extremities may disappear, even when softening of the brain or spinal cord has taken place. A sufficient number of accurately observed cases have now established this principle, which sets aside the more current opinion, that in all cases in which paralysis or spasm is transient, there is no structural change in the nervous centres. same time, it cannot be denied, that in cases of arachnitis, such lesions of motility are sympathetic, and depend on an irradiation of morbid influence. It is a practical principle that spasm generally indicates a state of irritation in the nervous centres, and paralysis the contrary.

A circumstance worthy consideration is, that while the bowels are torpid in diseases of the brain, the stomach is irritable. Vomiting, as has been seen in the cases detailed, is an usual symptom in arachnitis. It generally accompanies concussion of the brain, and those chronic diseases of that organ which induce pressure. The physiological explanation is, that the vagus is affected at its roots by irradiation from the diseased portion; but then comes the question, why are the gastric branches only affected? Why, in short, is there cerebral vomiting, but not a cerebral cough? There must be some as yet unknown anatomical arrangement of the twigs making up the vagus.

The termination of the sympathetic nerves in the brain is demonstrated by pathology. The heart, intestinal canal, and urinary organs, all parti cipate in the disturbance of the system caused by changes in the central axis. The pulse becomes irregular, the intestines torpid, the sphincter ani and bladder paralysed. The connexion between the brain and sympathetic system leads to remarkable modifications in the symptoms of certain diseases. Thus, in abdominal typhus, when active delirium sets in, the diarrhea, tenderness of the abdomen, &c., subside. If, in the course of a phthisis pulmonalis, cerebral disease occurs, and the patient becomes furiously delirious,-a complication we have occasionally observed, the cough, expectoration, and dyspnea disappear. We have heard a phthisical patient under these circumstances vociferate loudly, talk incessantly, be free from cough and from all rational signs whatever of disease of the lungs, when a post-mortem examination, made within forty-eight hours, has revealed the most extensive tubercular disorganization, so extensive, indeed, that there did not appear six inches square of healthy lung in the whole chest. In the same way we have observed extensive pneumonia to run through its course altogether unobserved and unsuspected by the

practitioner in ordinary, until the stethoscope has demonstrated to him. the presence of great and irremediable disease within the thorax. Again, we have observed a peracute gastritis to coexist with arachnitis: the stomach has been found after death so injected as to resemble a piece of red velvet, and yet during life there was not one symptom observed that could be traced to a morbid condition of that viscus.

Some of these complications may accelerate the fatal termination in arachnitis. The influence radiated on the pulmonary branches of the vagus may be so great as just to arrest irritation of the incident excitor nerves, and to prevent fits of coughing, but may not paralyse the organic nerves, and stop secretion. Then the mucus accumulates in the bronchi, and the patient dies at last suffocated. This state of things may not exist during the waking condition, but may, and indeed often does, supervene with sleep. In these cases sleep is dangerous, and, if the patient be not roused from it from time to time, will terminate in death.

Dr. Neisser insists that encephalitis never occurs except as the result of mechanical injuries, or as a complication of arachnitis, when it is confined to the portion of brain adjoining the inflamed membrane. The same remark applies to myelitis. But, under the term arachnitis, he means to describe a disease which has its true and primary seat in the pia mater, and which implicates the arachnoid membrane consecutively. The latter he looks upon as pathologically the cellular tissue of the pia mater. These membranes conjoined form the substratum of all idiopathic inflammation within the encephalon, while inflammation of the dura mater and of the substance of the brain follows only on mechanical injuries. We state these opinions doubtfully, and rather with the intent that our readers may know what is current among German pathologists, than for their adoption and approval. If the new views could be entertained which describe the arachnoid as a membraneous plexus of organic nerves, the pathology of the serous inflammations we have discussed must have a complete and minute reviewal. Possibly, indeed, there may be a clue obtained in this way to those inappreciable changes in the brain which give rise to delirium and other sensorial phenomena.

We have now to state in conclusion, that, after a careful perusal and analysis of Dr. Neisser's volume, we find it to be a valuable contribution to the natural history of disease. We cannot, indeed, recommend a more efficient plan than that which he adopts for the elucidation of obscure points in, and the general advancement of, pathology. The estimate of the symptoms, and their relations from the results of experience and the data of physiological science must be peculiarly rich in results. There is one great defect in Dr. Neisser's method, and that is, no attention is given to the etiological relations of the diseases he describes. We find no che

mical analysis of the urine, no investigation into the condition of the blood, no consideration of the causal antecedents. The whole treatment is unmitigated empiricism.

ART. IX.

On Disorders of the Cerebral Circulation, and on the Connexion between Affections of the Brain and Diseases of the Heart. By GEORGE BURROWS, M.D., late Fellow of Caius College, Cambridge, Fellow of the Royal College of Physicians, London, Physician and Lecturer on the Principles and Practice of Medicine at St. Bartholomew's Hospital.London, 1846. 8vo, pp. 220.

THE sensations experienced by all persons on placing the head in a dependent position, or on otherwise favoring congestion of the cerebral vascular system, are so determinate, that it has been almost universally received as a fixed principle, that the amount of blood within the cranium may be increased. And yet it cannot be denied, that an opposite opinion has been broached and advocated, for it seems to be a general law in metaphysics, that every principle, whether true or false, shall have its antago nistic principle. In the present work, Dr. Burrows aims at a twofold object he proposes to show, firstly, that this opposite opinion is erroneous; and, secondly, that changes in the circulation within the cranium have a much wider pathological scope than they are generally supposed to possess.

The doctrine that the quantity of blood circulating within the cranium is, under all circumstances, a fixed quantity, is an offset from the iatromathematical school of Borelli, and was promulgated by Dr. A. Monro at Edinburgh during the latter half of the last century. It was founded upon the incompressibility of the substance of the brain, and upon the spheroidal form of the skull. The idea might probably be traced from Monro to Boerhaave, or Pitcairn, or to some of their disciples. When, however, the last of the iatro-mathematical school had disappeared, we find Dr. Kellie taking up and defending this one of its doctrines which Monro had promulgated, and enlisting the late Dr. Abercrombie amongst his disciples. The name of Dr. Abercrombie was a tower of strength, and gave renewed vigour to the iatro-mathematical views. Dr. Clutterbuck adopted them in his article on Cerebral Apoplexy, in the Cyclopædia of Practical Medicine,' and even Dr. Watson, in his very recently delivered Lectures, maintained the invariableness of the quantity of blood in the brain, adducing the argument which Dr. Pitcairn, or even Borelli, would probably have advanced. "This depends," remarks Dr. Watson, "upon the mechanical structure of the cranium, and is capable of explanation upon the known principle of hydraulics." It is but justice to Dr. Watson, however, to observe, that in the second edition of his Lectures, he acknowledges a change of opinion on this point in consequence of Dr. Burrows's demonstration to the contrary.

The above history of this heresy, sketchy and slight as it is, shows that erroneous ideas reappear like weeds, and are as apt to perpetuate themselves in the soil of science. Dr. Burrows was impressed with the idea, that the opinions promulgated by Dr. Kellie and his successors were erroneous, and that they obscured the pathology of a most important organ; he therefore repeated the experiments of Dr. Kellie, and in the present work we have the results of his inquiries. These results, as well

as the pathological views of Dr. Burrows, we now propose to place before our readers.

Dr. Kellie inferred from his experiments-1, that a state of bloodlessness is not discovered in the brains of animals which have died by hemorrhage, but, on the contrary, very commonly a state of venous cerebral congestion; 2, that the quantity of blood in the cerebral vessels is not affected by gravitation or posture of the head; 3, that congestion of the cerebral vessels is not found in those instances where it might be most expected, as in persons who die by hanging, strangulation, suffocation, &c.; 4, that, if there be repletion or depletion of one set of vessels (arteries or veins) in the cranium, there will be an opposite condition of the other set of vessels.

In examining these experiments analytically, Dr. Burrows clearly shows, that they do not bear out Dr. Kellie in the inferences he deduced from them, and that, in fact, Dr. Kellie did himself at first draw the inference that the brain of animals might be depleted by bleeding, and their vessels drained of a very sensible proportion of the blood contained in them. It was in a subsequent communication to the Medico-Chirurgical Society of Edinburgh that he contradicted himself. It appears that his experiments stand alone, and have not been repeated: Dr. Burrows's researches are therefore the more interesting. We subjoin the first in extenso :

"On the 11th of January, 1843, I killed two well-grown rabbits. The one (A, plate 1), by opening the jugular vein and carotid artery on one side of the throat; the other (B, plate 2) was strangled. Each animal died violently convulsed. A ligature was drawn tightly round the throat of the rabbit (A) immediately it expired, to prevent any further escape of blood from the vessels of the head. The rabbits were allowed to remain twenty-four hours on a table, resting on their sides.

"While the blood was flowing from the rabbit (A), the conjunctiva was observed to become pallid and the eyeballs to shrink within the sockets. Upon the examination of the head of this rabbit, the integuments and muscles appeared blanched and exsanguined. Upon removing the upper portions of the cranium, the membranes of the brain were found pallid, and scarcely the trace of a bloodvessel was to be detected on the surface of the brain. The longitudinal and lateral sinuses were nearly empty of blood, and their course was not denoted by any colour of blood. Upon making sections of the brain, the interior appeared equally exsanguined.

"Soon after the cord was drawn tight round the throat of the rabbit (B), the conjunctival vessels became congested, the eyeballs turgid, prominent, and even projecting beyond the margin of their sockets. The integuments and muscles of the bead were found full of blood. Upon opening the cranium, the superficial vessels of the membranes, as well as the sinuses, were full of dark liquid blood. The whole substance of this brain and its membranes appeared of a dark reddish hue, as if stained by extravasated blood. The contrast between the two brains in point of vascularity, both on the surface and the interior, was most striking. In the one scarcely the trace of a blood-vessel was to be seen; in the other every vessel was turgid with blood." (p. 13.)

Dr. Burrows has appended coloured drawings of the post-mortem appearances in the brains of the two rabbits, and they are certainly in striking contrast. He observes, however, that the brains of sheep slaughtered by butchers are much less depleted than the brains of rabbits killed in the mode he describes. This difference is owing, he thinks, to a difference in