CHAPTER XX.

IMBECILITY AND IDIOCY.

THE Congenital mental deficiencies known under the designations of imbecility and idiocy are considered, as a rule, in connection with insanity in works on mental diseases. They are different only in degree from the degenerative insanities into which they graduate through several separate types. We can here include those cases that originate in diseases or accidents in early infancy as well as the congenital forms; they differ only in the stage of development at their incipiency, and their symptoms and prognosis are practically the same. The conditions of disease that pro

duce these forms of mental defect are those that inhibit or prevent the normal development of the brain, such as eclampsia, hydrocephalus, meningitis, etc. The congenital cases are those of brain defects from imperfect or abnormal development, as in porencephaly, macrocephaly, microcephaly, abnormal cortical development, reversions, etc.; absence of important parts, such as the corpus callosum; absence of special lobes, particularly the frontal ones; defective cellular development of the cortex, etc. To these we must add the effects of autotoxins, as in the case of myxedematic idiocy, where the absence or imperfect function of the thyroid gland is the cause of the mental as well as the physical symptoms. In some cases it is impossible to determine readily during life the nature of the pathologic process, and after death the macroscopic evidence may be also lacking. It is probable that in these cases the defective development of the cortical cells will be found to be in fault when microscopic examination is

possible. Besides this fetal or undeveloped condition of the cortical cells (Bevan-Lewis, Middlemass), we have also an actual reduction of their number (Hammarberg), and we can assume that, at least in a large proportion of cases of imbecility, a lack of functionally active cortical cells is the essential pathologic condition.

The external physical stigmata of imbecility, and especially of idiocy, are generally prominent. Thus, we have microcephaly, on the one hand, and the overgrown hydrocephalic or hypertrophic cranium on the other; the peculiar features and misshapen head of the Mongolian type, the dull expressionless facial development, the misshapen or defective auricle, the deformities of the jaws and teeth, facial and bodily asymmetries, and other characteristics that can be noticed more in detail in connection with the special varieties to be described. In the lesser degrees of imbecility these are not, as a rule, so prominent, but they usually exist, and are more or less noticeable and significant.

Considering first the milder types included under the head of imbecility, we may define, symptomatically, the condition as a state of cerebral defect characterized by a more or less limited intellectual or moral deficiency, making the subject to a noticeably greater or less degree below the average in these respects. These are the special marks of imbecility; other brain defects are not essential or characteristic. An individual may be deprived of one or more of his or her senses; in fact, so many of them may be lacking as to largely cut off the avenues for impressions from the external world, as in one or two very noted cases, and yet be very far from being an imbecile. It is the intellect, the judging faculty, or the associated moral impulse that must be affected. In most cases both the intellectual powers and the moral sensibilities are affected together; when the latter alone suffer or are lacking, we have the

typical moral insanity, which, though really a variety of imbecility, is noticed elsewhere as a separate type.

In many cases of the milder or less marked types of imbecility, the semi-imbeciles, as they have been called, there are no very pronounced external stigmata; they look and act to a large extent like normal individuals, and they may be able to fill a humble place in society where no great demands are made upon their intellectual powers. In infancy they may appear much like other children, and it is only in their later want of development that their disability becomes noticeable. They never really pass beyond the stage of childhood mentally, though their physical development may be good. In some respects they are even below the childhood standard; their capacity for learning is very limited, at least, in most directions, though they may show special aptitude in certain lines. Their sexual development is marked, and they are apt to be masturbators or perverts. Morally they are also deficient; they are apt to be unreliable and untruthful, and subject to fits of passion, and these with their sexual impulses, mentioned above, may make them dangerous to society. Under judicious control it is often possible to make them useful to a certain extent, and even self-supporting, but this is not usually possible when they are left to themselves.

These are the most familiar cases, the ones that show their deficiencies least. The majority even of these semi-imbeciles are markedly degenerates, and show it in obvious physical signs-misshapen crania, defective ears, jaws, and teeth, bodily asymmetries, and other stigmata of degeneracy. There is usually no very well-drawn line as regards the mental symptoms between these and those more favored in a physical point of view; but the more pronounced the bodily defects, the more marked are the mental and moral deficiencies. That this is not always so, does