in the fourth ventricle would affect the upper part of the spinal chord, and difficult respiration would take place.

From these cases, it would appear that extravasated blood in most instances, is not sufficient to arrest life in the sudden manner generally supposed, and that water in the brain cannot be considered the proximate cause of disease when all the train of symptoms which it is said to produce, can occur without its presence. There must be some other cause acting upon the coverings and substance of the brain itself.

In one hundred cases of apoplexy, which M. Serres examined, the meninges or the substance of the brain were affected. The quantity of effusion depends upon the nature of the inflammation. If it be chronic, it will be great; if very acute, there will be none at all. But the disease may occur from aneurism of some of its vessels, producing great extravasation, and death instantly ensue. This may be from the stimulus of distention being suddenly removed, occasioning collapse. We observe the same in removing water from the brain by puncture, or on discharging too much in spina bifida; in the sudden evacuation of dropsy of the abdomen. do not say that extravasation never destroys quickly by pressure; but from the fact, that large quantities of blood have been discovered upon the brain without disturbance of its function, it must be a more rare event than symptoms would lead us to suppose.

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As far as we are able to judge, there is a specific irritation of the brain, which manifests itself during the periodical revolutions to which the body is subject. M. Portal mentions the case of a woman, who constantly experienced convulsions just before the accession of the catamenia. That disease was more liable to return at stated periods than others, was so apparent, that the ancients believed the celestial bodies had great influence.

It is very evident, that epileptic attacks oecur without any previous warning, assuming the very worst form of apoplexy. Dr. Cheyne says, "from the 12th of May to the 19th of August, I was called to nine cases of apoplexy, and the summer was the most sultry I ever knew; and as far as I know, the

only quality of the season upon which this disease depends, is extreme heat." Great cold, as well as excessive heat, is considered an exciting cause of the disease. In the first, the expansion of the fluids is supposed to produce it; and in the second, the retreat of the circulation to the internal parts of the body. But it has been shown, that the brain is incompressible, and that it admits of no more blood at one time than the other, and therefore it could be effected by neither.

If this view of the pathology of the brain be correct, the practice to be deduced from it is, 1st, the use of moderate bleeding; 2d, counter-irritants; and 3d, active purgatives.

Dr. Cheyne says, "two pounds of blood ought to be removed as soon as possible after the attack, and if the first bleeding has not been of service, and the disease is unequivocally established, the chief question to be decided, is the additional quantity of blood to be drawn. It ought to be known, have been taken from

that from six to eight pounds of blood a person by no means robust, before the disease which ended favourably, began to yield." If the repetition of bleeding as advised here, be practised, the system becomes so prostrated, that should the patient be so fortunate as to escape, some other disease will be induced. If we bleed until some impression be made upon the disease as it is called, we shall in all probability seat it more firmly. The experiments of Dr. Pring, as before stated, prove it to be impossible to diminish the quantity of blood in the head. If the system loses such a vast quantity of stimulus, debility principally falls upon the venous circulation, and the pressure is actually kept up by it. But this excessive bloodletting is productive of another injurious tendency. Complete syncope is often induced and the bleeding is continued, mistaking the effect for the cause: re-action from exhaustion. As soon as the patient recovers a little, this re-action shows itself in accumulated blood about the right auricle and ventricle, which cannot evacuate themselves; the blood cannot be transmitted through the lungs, on account of impeded respiration; the jugular veins become turgid and the face is livid; the carotids throb, and there is beating in the head. Bleeding is again urged, and the case terminates fatally, and dissection

shows the distended state of the vessels, which causes the attendant to regret, that depletion had not been carried to the extent demanded by the urgency of the case. Dr. Seed bled animals to death, and found in almost all instances, effusions of serum, and even blood in the brain. This, no doubt, is the reason we see so many histories of apoplexy. If examination shows serum or extravasated blood after death, it is always imputed to disease, and not to the lancet.

It appears proper that bleeding should be carried to an extent sufficient to take off the distention of the vessels, and restore the circulation to its equilibrium. Dr. Fothergill says, bleeding in apoplexies is one of those operations, which, on several accounts, requires the most dispassionate consideration. In no disease is the judgment of the prescriber of more consequence to the patient." If apoplexy be a simple distention of the vessels, or if it be a congestion in one part of the brain, the evacuation of blood should not be large. It is so difficult to determine between re-action from exhaustion, and irritation of the brain, that the utmost circumspection is necessary. It is safer to rely upon active counter-irritants upon the bowels and skin.

It seems to result from the preceding investigation, that the brain is incompressible or nearly so; in consequence of which, the blood in that organ cannot be sensibly diminishedthat effusions of blood, serum, and water, do take place without impairing the functions of the mind-that no pressure upon the cerebrum or cerebellum produces any sensible impression -that it is the indirect pressure upon the spinal chord that gives rise to difficult respiration-and lastly, in a practical point of view, these deductions will lead us to avoid those excessive bleedings, which are the cause of confounding apoplexy with re-action from exhaustion, which these large evacuations bring on; and in the treatment of hydrocephalus, as there is no symptom which can positively inform us when effusion has taken place, our endeavours shouldbe unremitted in the continuance of means, even when the case is apparently hopeless. They will also cause us to be on our guard against those transmitted irritations, which are so frequent, so decep

tive, and so embarrassing, and give close circumspection to diseases of the bowels in children, as the brain is almost always the first to be affected sympathetically, producing irritation, and at last disease of that organ.

ART. III. On the Nature of the Compounds, usually denominated Chlorides of Soda, Lime, &c. With Remarks on their Uses as Disinfecting Agents By LEWIS C. BECK, M. D. Professor of Chemistry in the Vermont Academy of Medicine.

THE chief design of the following communication is to inquire into the nature of those compounds which have been called, as I conceive improperly, Chlorides, or Chlorurets of Soda, Lime, &c. As tributary to this object, I shall also notice the manner in which these compounds are obtained, and their mode of operation as disinfecting agents.

PREPARATION.-There is nothing peculiar in the preparation of the compounds under consideration. All that is necessary is to subject the hydrates or solutions of potassa, soda, lime, and indeed any of the fixed alkalies or earths, to the action of a current of chlorine gas. If, instead of these, we pass a stream of the gas through solutions of the carbonated alkalies, equally efficient compounds are produced: and we shall hereafter see that other salts may also be employed for the same purpose.

The substance which has received the name of Labarraque's disinfecting liquid, is prepared according to his own formula, as follows:-2800 grains of crystallized carbonate of soda are dissolved in 1-28 pints of water; being put into a glass, two-thirds of the chlorine evolved from a mixture of 967 grains of salt with 750 grains of oxide of manganese when acted upon by 967 grains of oil of vitriol, previously diluted with 750 grains of water, are to be passed into it.*

* I quote from Mr. Faraday's paper on Labarraque's liquid in Brande's Journal, New Series, Vol. II. 84, not having the original formula at hand.

The liquid may also be obtained in the manner proposed by M. Payen, which consists in the mutual decomposition of chloride of lime and carbonate of soda. But this method will seldom be employed, as all the valuable purposes of the article can be attained by the employment of the compound of chlorine and lime alone. This is now so extensively employed in the process of bleaching, that there is little difficulty in obtaining it at any time. When it cannot be procured, however, solutions of lime or soda may be easily charged with chlorine gas in the manner represented in the annexed cut.

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Into the florence flask introduce manganese, common salt, and dilute sulphuric acid in the proportions above mentioned, taking care that it is not more than a third filled. The bottle may contain lime water, or solution of soda or its carbonate; and should be kept at the temperature of 60° Fahr. or below. Having now adjusted to the flask a bent tube, with one leg passing to the bottom of the vessel containing the solution, the heat of a lamp, or a few coals, is to be applied to the flask. By this means chlorine is evolved, and is absorbed by the solution. The heat should be continued until the evolution of chlorine has nearly ceased, which will generally be from fifteen to twenty minutes. The clear fluid is now to be decanted. This is the disinfecting liquor.

This disinfecting compound may therefore be obtained in either of the following ways: