insanity, it is not always the effect of conversion; but is frequently the simple translation of a morbid action from a diseased part to the brain, where the effect produced is a distinct and dissimilar affection:-it is, in fact, mere metastasis, not conversion. If effusion follow inflammation, this is not the conversion of one disease into another, but the natural termination of the original disease.

When insanity has ensued by conversion, it has often proved a salutary operation, as far as bodily health and a means of prolonging life are concerned.

Insanity produced by conversion from other diseases, is probably always arising from the change of determination of blood from the part or parts originally affected to some part of the encephalon; and is a link in the chain of phenomena derived from excessive local momentum of the arterial system. When these conversions succeed each other, or alternate, they may be suspected to proceed from excessive determinations shifting from one part to another.

This mode of terminating a disease may sometimes be anticipated by a nice observer. When the indication. of a new and not dangerous malady appears in a case of insanity, it should be encouraged; since, if it be established, it probably will relieve or remove the mental derangement, unless that originate in some organic or mechanical cause. The prognostic will be more certain when there is a natural relation of the new disease to the primitive one. Thus, when a disease owes its origin to irritation producing stimulation and excitation, it is often removed by applying counter-irritants to some part of the body, and there producing analogous stimulation and excitation. Such applications act by derivation. Among the artificial means of accomplishing this end, are setons, issues, the moxa, caustics, blisters, emetic tartar applied externally, rubefacients, &c.: salivation, whether spon

taneous or artificial, is of this class of remedies: the natural and most common means is hydropic effusions. By any of these modes, probably, the balance of the circulation is restored, and also the reciprocal action of the nervous and vascular systems; and hence often the cure of insanity.

Of all changes of diseases, that of insanity into dropsy is perhaps the most frequent. But agreeably to the conclusion, that insanity is the effect generally of preternatural determination and consequent excitation, effusions of fluids must be considered as natural terminations of super-excitation, and not as conversion of one into another disease. An exception, however, to effusion proving a cure to insanity seems to obtain, when the deposition occurs within the brain or its envelopes. Effusion into other parts immediately relieves the excessive momentum of arterial action, by the capability of surrounding parts to accommodate the effused fluid without much disturbance to the functions they exercise, and the facility with which the absorbents remove it. But when effusion is consequent on great vascular excitation in the brain, it is otherwise; for the accumulated fluid has no vent into contiguous parts, and the absorbing vessels being fewer in that organ, it is not so readily taken up. Consequently, the quantity of blood flowing within the encephalon is diminished, and hence the co-operation of the nervous and vascular systems is no longer maintained.

When dropsy has been converted into mania, it has been ascribed to the increased power given to the absorbent and secerning vessels, by the augmented stimulus of the sensorium, by which the morbid action producing intellectual disorder has been induced.

Unquestionably, what adds tone to any set of vessels, may enable them to recover from or shift a morbid action. The increased action, therefore, in the vessels of a parti

cular part which has caused effusion may cease, when that effusion, which is the effect, is completed; but still, the balance of the circulation not being restored, a diseased action may arise in the brain, and occasion mania; and there, although effusion occur, yet, for the reasons adduced, the mind is not thereby restored to sanity.

The mental derangement induced by these conversions is sometimes simple delirium, sometimes real mania. The first is generally the consequence of febrile excitement; but the latter is without fever, and is probably, when from conversion, the effect of a change of site of a morbid action. If it be the delirium of fever only, it will cease with its cause; if it be mania proceeding from the latter cause, and fever supervene, and the intellects should recover during the progress of fever, there may be some danger of relapse at the cessation of it. On the contrary, if the powers of reason gradually unfold as fever declines, or after it has altogether ceased, the sanity may be perfect and permanent. These are very important considerations, and should never be lost sight of by those who study the nature and phenomena of insanity.

Such are some of the diseased conditions of the human body, which primarily or secondarily induce, or alternate with, or succeed, insanity.

Even this brief notice of them, and the probable intervention and influence of their mysterious agency, if it do not explain, points out the sources of many morbid actions in organs remote from each other. It likewise shews the relation of several diseases one to the other, and especially to insanity, and the facility of conversion, which further exemplifies their connexion.

Notwithstanding some attention has been recently given to the conversion of diseases, it is a subject which presents a wide field for observation; and when more

fully investigated, many morbid phenomena, which are now regarded as mysterious, will be explained.

Hence, every one must be convinced how much it behoves him, before he attempts to remove even insanity, to reflect upon the probability, whether, in so doing, he may not produce a worse, that is, a fatal disease. I am quite certain I have seen several cases of mental derangement occasioned by a too busy interference with the processes to which nature resorts for the restoration of health.

COMMENTARY XI.

FATAL DISEASES CONSEQUENT ON INSANITY.

THERE are certain morbid conditions to which the insane are especially prone, and which generally terminate in death these, therefore, constitute an important part of the pathology of insanity.

Some, as apoplexy, paralysis, epilepsy, and other cerebral affections, I have shewn are frequently the causes of mental derangement, or become complicated with it, and that they are likewise sometimes the consequences of it. Whether, however, the cause or effect, I have nothing further to observe, except that they often prove mortal.

But as insanity is proved also to be a malady tending, either directly or indirectly, to shorten life, through the influence of certain diseases, I shall briefly particularise those affections. Their characters, as well as frequency, necessarily vary with the duration of the maniacal action and the situation of the patient.

Individuals who, possessing the means, have assistance as soon as symptoms of disease appear, preserve the identity of their maladies. In large communities of the sick, however, every medical observer must have remarked the singular extension and peculiar effects of some maladies on the constitutions of the patients, and that diseases often there assume characters quite anomalous and unknown in private practice.

So in regard to the insane: in very small establishments the character of the diseases generally attacking them differs materially from those which they experience when congregated in large numbers.