PHRENITIS.

By the term PHRENITIS is understood an inflammation of the brain and its membranes. When the inflammation is supposed to be confined to the former, the term Cerebritis ; and when to the latter, Arachnitis has been very commonly applied. The symptoms, however, arising from the affection of these different parts run into each other; and even if they were in themselves distinct, still their almost necessary combination in most cases, and the easy transition from one to the other, owing to the proximity and intricate connexion of parts, would produce an intermixture of symptoms, such as in practice could scarcely admit of separation. Some authors have even gone so far as to consider the term Arachnitis too general, and have adopted the still more exclusive appellation of Piitis, when the pia mater has been the presumed seat of inflammation. But if there be difficulty in distinguishing between the inflammation of the brain and its membranes generally, still less can we be expected to point out with accuracy the symptoms which bespeak inflammation of one or the other portion of the arachnoid or the pia mater: indeed the cerebral portion of the arachnoid and the pia mater are so closely united, that one can rarely suffer inflammation without implicating the other. For practical purposes, inflammation of the membranes of the brain may with propriety be treated of under the term

ARACHNITIS.

The most acute form of phrenitic disease is generally dependent upon inflammation of the membranes; and when idiopathic, it is usually the pia mater, and that part of the arachnoid which covers the brain, which are involved; while the arachnoid lining the dura mater suffers more particularly

when the inflammation arises from injuries or disease set up in the bones of the cranium.

The symptoms of acute inflammation of the membranes are rigors and general febrile disturbance, intense headache, suffusion of the eyes, intolerance of light and sound, pulsatory or other sounds within the head-sharp, quick pulse-quick, hurried, and altered mode of speech and action-furious delirium, convulsion, and coma.

But while these may be stated as the general symptoms of the confirmed disease, it must be remembered that it varies much in the mode of its approach, as well as in the intensity of its progressive stages. Sometimes the most unequivocal symptoms at once develop themselves; but more frequently several days of general uneasiness, such as belong to many febrile and inflammatory affections, precede the more decided symptoms; and to this are added a dull heaviness of the head, a weary aching of the eyes, occasional shiverings, a loss of appetite, and a feeling of nausea, often succeeded by sickness and vomiting; the urine scanty and high-coloured; the bowels constipated; the pulse generally quick, yet variable in frequency as well as in strength.

Such symptoms, although they mark inflammation already commenced and making decided progress, may be considered the first stage of Arachnitis; and in reference to the more severe symptoms about to follow, may be viewed as precursory; and having continued for an uncertain time, a few days or a few hours, the dull heaviness of the head gives way to an intense pain, and the conjunctiva becomes injected with innumerable minute vessels, producing the appearance called the ferrety eye. As long as the patient is able to explain his feelings, and is not led by the confusion of his mind to neglect or forcibly resist his

bodily sufferings, he shows distinctly an aversion to all loud noises or strong light; and expresses, when asked, in the most decided terms, the violence of his headache, and the harassing sounds within his throbbing temples. His pulse is sharp, quick, and hard, but even now is subject to occasional more deceptive variations-the skin is hot and dry, but occasionally bursts into perspiration; and this is sometimes even profuse. The tongue is white and parched, with red tip and edges; and when shown, is protruded with unnatural vigour, or is observed to quiver and vibrate. The manner of the patient is flighty and inconstant; he sometimes bursts into paroxysms of violence-sometimes falls into a drowsy state; but natural and sound sleep are altogether wanting. The state of excitement and delirium continues and increases, till, after a very few days, this second stage gives way, either suddenly or by slow degrees, to the exhaustion of the third stage, when the pulse permanently loses its power. The raving delirium is succeeded by a still less healthful condition of the mind, which becomes lost in confusion, and the patient lies in a state of unconscious prostration, his tongue dry, brown, and chapped, his teeth loaded with sordes; the face, the eyes, and the hands begin to show spasmodic twitchings; severe convulsions presently affect the whole body, and a state of coma, for a few hours, precedes the dissolution.

Morbid Appearances.-The morbid appearances vary according to the continuance of the disease, its severity, and the part chiefly affected. In genuine Arachnitis, where the arachnoid covering the brain and the pia-mater have been the seat of inflammation, increased vascularity may be the only deviation from health observable. This is sometimes general, sometimes in patches, or sometimes occupies one hemisphere. Unless the vascularity be in a very marked or excessive degree, it is always open to some doubt; as the

position in which the head has been placed soon after death, or the circumstances of the last moments of life, may influence the injection of the vessels; but where we not only find the larger vessels filled, but the smaller ones much more numerous than usual; and still more when we find in any portion of the membranes some of the more decided products of inflammatory action; the vascularity becomes a more important and undoubted indication of the extent of that action. In some instances of unusually intense vascularity, without the occurrence of other proofs of acute inflammation, the action has been of a more chronic character.

Other proofs of the early stages of acute inflammation are derived from unusual dryness of the surface of the arachnoid, or a peculiar unctuous condition of the secretion, and an unnatural softness or friability of the membrane; so that it is with difficulty taken from the brain without tearing. As the inflammation advances, serous effusion is seen filling the spaces between the convolutions, and apparently penetrating the structure of the pia mater as it dips into the fissures. The membranes themselves become thicker and firmer than natural, and opake spots are seen following the course of the larger vessels. These changes are frequently more observable at the base of the brain, about the cerebellum and the pons Varolii, or around the optic nerves, than on the surface of the hemispheres ; and on these parts they often produce a gelatinous appearance, which, however, is deceptive, as the fluid has seldom acquired any unusual consistence, but escapes slowly, owing to the loose cellular tissue in which it is there collected being somewhat increased and thickened by inflammation. The same changes, both in the character of the secretion, and in the tenacity or density of the membrane, are also observable throughout the ventricles.

With regard to these appearances, it may be observed,

that generally, in proportion as the effusion is greater on the surface of the hemispheres, and more especially in the ventricles, coma and cerebral depression have marked the concluding periods of life; whereas, when convulsive action has prevailed, the collection of fluid and the evidences of inflammation are greater at the base.

It occasionally happens that the character of the effusion beneath the arachnoid is completely changed: it becomes opake, of a straw colour, and is apparently pus; and when the arachnoid and pia mater are raised from the brain, this is raised with it amongst the meshes of the pia mater, by which membrane it seems evidently to have been formed. Although this is occasionally discovered as the result of idiopathic inflammation, it is more often the consequence of some mechanical injury, as blows and fractures of the basis. Where pus is found upon the surface of the arachnoid, the mischief may likewise generally be traced to disease of the cranium and dura mater.

In the progress of Arachnitis, the surface of the brain itself necessarily becomes involved; the vascularity of the cineritious substance is increased, and its texture is softened; and this frequently in a very appreciable degree.

The Diagnosis in this disease is most important, and at the same time most perplexing. The three diseases from which it is most difficult to distinguish Arachnitis, are fever, acute mania, and delirium tremens; and this difficulty is the greater, because each of these diseases is not unfrequently accompanied by some modification of inflammatory action in the membranes of the brain; so that each of them may pass, by almost insensible gradations, into true Arachnitis.

The cerebral affection in fever is generally marked by much more evidence of oppression than the delirium of Arachnitis-fierce and active delirium rarely occur in fever,