SEMEIOLOGY OF DISEASE OF THE BRAIN - in no department of medicine is diagnosis more obscure than in that upon which we now enter. Inclosed within its bony case, alterations in brain structure corresponding to phenomena during life can never be discovered till after death, when it is much more difficult to trace their connection ; and numerous and diversified as are the functions of the organ as a whole, physiologists have yet failed to determine, with any degree of accuracy, the particular regions in which its various powers are developed, or the special uses of many of its parts. The theories of Gall and Spurzheim, had they been based on any sufficient groundwork of fact, might have rendered essential service in discriminating the site of dis eased action ; but experience has shown that perversions of those mental functions which form the basis of their system do not de pend upon, or even correspond with, lesions of the brain in those regions to which the names of organs have been assigned ; and it yet remains to be proved that special portions of matter are at all necessarily connected with particular actions of mind.
In addition to these difficulties we find one set of head symp toms, so transitory in their character, that we'cannot suppose them to depend on change of structure; while others, though more per sistent, leave no trace for the observation of the anatomist : both of these must as yet be considered simply as disturbances of func tion, though they sometimes approach so nearly to the symptoms of structural disease, that it is very difficult to distinguish them. On the other hand, the evidences of structural disease of very different kinds are so exactly analogous, that the physician is at a loss in endeavoring to assign to each its exact cause : no less perplexing is the circumstance that the obscurity of the mental faculties in many of these conditions of disease deprives us of the aid which a true account of the patient's sensations might afford, as they are blunted, or perverted, or the power of analyzing and describing them is lost.
For the same reason, it is not unfrequently impossible to obtain a history of the case at all available for the purposes of diagnosis; and yet no part of the inquiry is more important. Impracticable
as the exact discrimination of symptoms may be at the time of observation, each case is generally marked by successive features in its history which, if they have been properly noted and care fully studied, will throw most important light on its character and causes.
The pathology of the brain is much less understood than it ought to be in the present day, in great measure, I believe, because the importance of the antecedent phenomena has been underrated, and the symptoms have been read apart from the history. Abercrombie is deservedly one of the great authorities on diseases of the brain; but the principles of diagnosis cannot be learned from his work on this subject, because, in most in stances, the previous history of his oases is so meagre. Let it be remembered, too, that in the present state of our knowledge this record of the symptoms during life is, in many instances, all that is really known of the disease, all that is really valuable in treat ment; and thus, in this case, diagnosis becomes, as it ought to be, the handmaid of practice.
Mental alienation forms another element in the consideration of diseases of the brain, which is, as yet, very much beyond the reach of pathological research. Without speaking dogmatically, it may be affirmed that scarcely any lesion has been found in cases of insanity which has not also been present in instances in which the mind has been perfectly clear. We must be content to acknowledge our ignorance in this matter; and if we can trace out general resemblances, and classify cases according to some well-known types—more especially if we can discriminate the cases in which structural change exists from those in which it is not necessarily present—we shall have done all that we are justi fied in attempting.
It will probably simplify the study of the diseases of the brain if, before entering on their special diagnosis, this chapter be de voted to an exposition of the symptoms which are more directly derived from the powers of innervation, as they refer to the mental faculties, and the centripetal and centrifugal nervous actions—the sensations and the muscular movements of the patient.