There is little doubt but that a diseased state of the brain exists previous to the accumulation of the water, and the great question is respecting the nature of this state. We have little reason to suppose it inflammatory, for the disease does not attack strong, healthy children, those over fed, or rendered plethoric by too great care. If there are any children peculiarly subject to hydrocephalus, it is the weak, the pale, and the debilitated. These indeed may suffer from venous plethora; but we ought to reflect that this is not a disease of their time of life. An accumulation of blood in the arteries, in a degree greater than the veins can carry off; veins, as we have seen, tortuous, and in which the motion of the blood is peculiarly slow, may occasion increased exhalation: but to this may be objected, that the early symptoms are not those of compression but of irritation only, of irritation not in the brain, but in the bowels. If we pursue the series of symptoms, we shall find that the consequences of compression are combined with those of irritation, but that the former are by no means in proportion to the quantity of fluid found in the ventricles after death. In this argument we lay no stress on the effect of remedies, for we believe all remedies equally ineffectual.

It is indeed probable that symptoms of irritation and compression may be relative to the constitution of the patient; that, as in the former case, a slighter cause may in a very irritable habit produce violent symptoms, so, in a more torpid system, a little degree of compression may produce insensibility or spasm. Yet these views will not lead us far, and very certainly will not assist us in the cure. The first symptoms show, as we have said, irritation in the bowels, which may be readily supposed to originate from, an affection of the brain: the second train are the effects of compression, which may be probably accounted for from the accumulation of fluid.

If, however, we apply these views to practice, we shall find their fallacy: the means of relieving irritation or compression are equally useless; and we see no means of accounting for the symptoms, but from supposing an original defect in the organization of some portion of the brain itself, - a cause which will be supported by its being often confined to particular families, and its often affecting the children of the same parents. What this defect is we cannot explain: but we have seen that a free communication between different parts of this organ is peculiarly necessary; and if we suppose this communication interrupted, the usual consequences of increased action will follow. We sec this deficiency of communication in the spina bifida; and children live for some time till the necessity of the free circulation of the nervous power is felt. A want of this free circulation in the brain itself may not be so soon experienced as in the nerves which supply the voluntary muscles; and according to the part where the. deficiency occurs, the disease may appear sooner or later. This idea is not supported by dissections; but, in general, if the vessels are found peculiarly turgid, or the ventricles preternaturally filled, anatomists have been contented with the success of their researches.

We rest with more complacency on this opinion, because it explains the want of success which we think has attended every plan. As authors, however, have had their favourite modes of relief, which they have sometimes thought effectual, it is necessary to describe them. Bleeding, according to the idea of Dr. Rush that the disease is inflammatory, has been practised; but on this subject Dr. Rush is certainly prejudiced. Where-ever he finds bleeding useful, he sees inflammation. It has escaped us if his practice has been imitated in this country, so that its success is equivocal. Topical bleeding, either by the cupping glasses or by leeches, under the influence of Dr. Quin and Dr. Garnett's ideas, we have employed with scarcely even temporary advantage. Blistering either on the vertex, the nape of the neck, or behind the ears, has been more useful, but has never effectually removed the complaint. Purging, in all its forms, has only afforded a slight and temporary relief. We have been told of the effects of mercurials, and have employed them actively, so as to raise a ptyalism; or more slowly to give permanent tone, or as purgatives. It has been said that they have succeeded; but we have unfortunately failed, though when a slight ptyalism has been produced, we have found the symptoms in some degree relieved: the fatal event, however, has scarcely been retarded, or retarded only. In one case, where we suspected the source of the previous complaints, we early employed calomel as a purgative. A very slight soreness of the gums ensued, and the disease even came on during the action of the mercury.

Digitalis, doronicum, and cicuta, have been mentioned; but, on examining the accounts of authors who have recommended these remedies, we have found little foundation for their employment, and cannot therefore speak of them from experience. The children subject to the complaint are, we have said, inactive and debilitated; and we should not, a piriori, expect any considerable advantages from narcotics. As the water is usually contained in the ventricles, an operation is wholly inadmissible.

When we consider the confident assertions of some authors, and compare them with the effects of the most careful trials, we shall find it highly probable that they have mistaken other diseases for hydrocephalus. We have certainly done the same, for we once thought mercurials effectual. In advanced life there are affections of the head not strikingly apoplectic, though similar to apoplexy, which require large doses of mercury, and are relieved by it.

See Whytt on Hydrocephalus; Quin on the Apo-plexia Hydrocephalica; Fothergill and Watson, London Medical Observations and Enquiries, vol. iv. and vi.; Withering on the Digitalis Purpurea; London Medical Transactions, vol. ii.; Monro's Observations on the Structure of the Nerves; Edinburgh Medical Commentaries, vol. v. vii. viii.; Medical Communications, vol. i. p. 404; London Medical Journal, vol. i.p 357; Memoirs of the Medical Society of London, vol. i. p. 165 and 169. Hydroc lstis, (from Hydroce Phalus 4285 aqua, and a bladder'). Encysted dropsy, or dropsy of a particular Part.