2. Would the Mental Deficiency respond to Medical Treatment?—Cannot the doctor prescribe something to cure the mental deficiency or want of balance? Let us give some consideration to this question. Medicines act either upon the symptoms of a disease, or upon the organic changes which produce them, or, lastly, upon the very causes of such organic changes. Quinine, for example, has a selective action on the parasites of malaria; mercury produces an undoubted effect upon syphilitic growths; treatment by cold baths keeps the temperature of typhoid fever below a certain level during the whole of the illness. Cannot analogous results be hoped for in mental deficiency? A brief résumé of what we know concerning the causes of mental deficiency and the anatomical lesions which accompany it will determine our answer.
The dominant etiological feature is that mental deficiency and want of balance depend upon hereditary conditions, or conditions acquired in the earliest stages of development. By hereditary conditions must be understood strictly those which result from alterations in the germ cells of the parents. An intoxication alone seems capable of exercising upon the latter a sufficiently general action to reach the germ cells, and by far the most frequent poison is alcohol. By acquired conditions must be understood the results of diseases of the fœtus or of infancy, and especially the cerebral complications of the infectious fevers—e.g., meningitis in the course of an eruptive fever. In all such cases, with rare exceptions to be mentioned immediately, by the time the mental deficiency is discovered, its causes are no longer active, and consequently cannot be affected by medical intervention.
The statements we have just made with regard to the causes of mental deficiency lead to some practical conclusions. The ultimate evolution of the congenital cases differs from that of acquired cases, and this renders a study of the early history of the child important. If the development of the child has been normal at first, and has then been abruptly interrupted, for example, by an attack of meningitis, of which we can obtain by inquiry a definite history, the prognosis is not good. For it is a well-recognised fact that cases of acquired mental deficiency are not likely to make a fresh start. If we were hesitating whether to send an imbecile child to an asylum or to put him in a class for mental defectives, a history like the above would lead us to give the preference to the asylum; but let us say once more, we do not find here an indication for treatment.
As to the changes which are found post-mortem, these are manifold and of an unalterable kind. They are as follows:
(1) The results of the rupture of a cerebral vessel—e.g., from asphyxia at birth or a delivery by forceps. Blood has been poured out into the nervous tissue. The latter has been destroyed over a greater or less extent, and there is found in its place a cyst filled with sero-sanguineous fluid.
(2) The obstruction of an artery—e.g., by septic thrombosis—has prevented the blood from reaching a part of the brain, with similar results to those mentioned.
(3) In other cases are found the more or less extensive changes produced by meningitis or meningo-encephalitis. The inflammation of its envelopes has interfered with the brain, and consequently with its functions.
(4) An increased secretion of cerebro-spinal fluid has led to a compression of the nervous system or a distension of its cavities, notably of the lateral ventricles of the cerebral hemispheres, and has led to a separation of the bones of the cranium, thus producing the large globular head of hydrocephalus.
(5) There may be found simply defects of development whose causes are known (microcephalus, or extreme smallness of the cranium relatively to the face; microgyria, or marked thinness of the convolutions).
(6) Lastly—and this is frequently the case in the worst degrees of deficiency—the post-mortem, and even microscopic examination of the organs may show no change at all.