FUNCTIONAL DISEASES OF THE NERVOUS SYSTEM If this principle is kept in mind, it will be readily seen why- heterogeneous symptom-complexes, due to a variety of etiologic factors, arc included in the same group of functional nervous diseases, and that the dividing line between functional and organic affections changes from time to time as our knowledge of pathogenesis increases, so that at the present day the classification of certain disease-types, such, for example, as chorea and epilepsy, among the functional diseases meets with objec tions which arc not altogether unjustified.
No one can doubt that for every functional disturbance there must be a corresponding anatomical change in the nervous system; but, in accordance with the fugaciousness of the symptoms, the pathologic lesions are in some way peculiar, and as yet we have no conception of what this peculiarity- consists in.
Aside front the pathologic viewpoint, from which we approached the subject in the beginning, functional diseases also possess certain common clinical characteristics which justify their classification in one large group. The most important characteristic, which is common to almost all functional diseases and on which the others appear to de pend, is that the symptom-complexes depend on a certain constitutional anomaly of the entire nervous system. This does not prevent the fact that certain definite symptoms—in harmony- with the broad principle of localization--do not have their seat in some unknown anomaly of a definite portion of the nervous system; but if We carefully examine the entire individual, both from the neurologic and the psychic stand point, and if we take his subsequent development into consideration, we will discover phenomena which cannot be explained on the ground of a single circumscribed localization of the morbid process. This will be explained more fully when we come to describe the neuroses, such as hysteria and neurasthenia.
If we follow out this conception to its logical conclusion, we will understand why the symptoms that are observed exhibit such a great variety in themselves, and vary to such a remarkable degree in the sante individual. This will also be explained later by means of illus
trative cases. It also affords an explanation of the fact that heredity plays a much greater part in the functional than in the organic nerv ous diseases. Thus not only direct similar inheritance from both par ents is observed in one or more of their children, as well as the family incidence of certain nervous diseases; but, on the other hand, we fre quently come across cases of dissimilar inheritance which challenge our attention. Finally, we are able to understand that the prognosis of fl single symptom is not identical with the prognosis of the disease as a whole, and that WO must be prepared for the sudden disappearance of one symptom and the equally sudden appearance of another that may- be quite different externally, although sprung from the same pathologic soil.
Any classification of functional nervous diseases, composed as they are of heterogeneous things, is necessarily more or less arbitrary. It seems to us wisest to erect two main groups. The first contains those diseases in which somatic symptoms are produced by anomalies in the psychic life of the individual, in which, as Wernicke has explained in the case of the psychoses, the association-system is the seat of thc disease. The type of this group is hysteria. The second group embraces all those functional disturbances in which we may expect to find a primary lesion of the projection-system. The representative of this group is chorea. Neurasthenia occupies an intermediate position be tween the two groups. It: symptomatology is much more pronounced than is the case in diseases belonging to the two groups mentioned, being composed of psychogenic or psychic and primary somatic dis turbances.
Since the psychic development is much less advanced in children than in adults, the second group, that of the primary somatic disturb ances, interests us chiefly in this connection, particularly as these dis turbances are the earliest that occur in childhood.
We shall accordingly begin our systematic exposition of the sub ject with the large symptom-group of the convulsive diseases.