Degeneracy: Its Causes, Signs and Results

by Eugene S. Talbot

CHAPTER XVI

Degeneracy of the Brain

One illustration, and a very striking one, of the influence of degeneracy on the brain is the durencephalous child which so often appears in degenerate families. Here the cerebral hemispheres and everything but the medulla and pons may be absent, while the rest of the body is in a comparatively normal state of development. Starting with such an extreme expression of degeneracy in the brain, a wide but closely linked range of deficiencies may be found in the brain of degenerates, involving even in some almost normal individuals more than simple deficiency. What was pointed out by Spitzka,[245] of New York, twenty years ago concerning the brain of hereditary lunatics, is equally true of the brains of the other degenerate branches of the same tree. The conventional notion associating idiocy and imbecility with quantitative deficiency of the forebrain only is, as Spitzka remarked, a very imperfect one. The researches of numerous observers have shown that qualitative defects (using the term qualitative in its wider sense to cover both morphologic and histologic aberrations) are as common, and are more characteristic features of the degenerate brain. These defects may be enumerated under the following heads: 1. Atypical asymmetry of the cerebral hemispheres as regards bulk. 2. Atypical asymmetry in the gyral development. 3. Persistence of embryonic features in the gyral arrangement. 4. Defective development of the great interhemispherical commisure. 5. Irregular and defective development of the great ganglia and of the conducting tracts. 6. Anomalies in the development of the minute elements or neurons (as the cells and associating of fibres are now generally called) of the brain. 7. Abnormal arrangements of the cerebral vascular channels. All of these conditions, separately or in the combination of several of the features above mentioned, are occasionally found in the brain of paranoiacs, moral imbeciles, criminals, deaf-mutes and other degenerates. Of the first type the brain (Fig. [111]), from the practice of Kiernan, is an excellent illustration. This brain came from a paranoiac criminal who died in the Chicago (Cook County) Insane Hospital. A very similar brain was observed by Kiernan in one of the paranoiacs dying in the New York City Insane Hospital. Similar brains have been observed in deaf-mutes[246] whose mental status passed muster because of the allowance made for mental deficiency due to deaf-muteness. A brain showing as great asymmetry was found in the case of a French physician of standing who was a member of a mutual autopsy society. He proved, however, to have had degenerates in his ancestry and had exhibited peculiarities which showed that much of the degeneracy due to this ancestry had been corrected by proper training. The defects enumerated under Spitzka’s second head are also observable in the illustration given. The gyres are not only asymmetrical as to their number in the two hemispheres, but also as to their size. The contrast between this brain and the ideally normal one of the mathematician Gauss[247] (Fig. [112]) could not well be greater. Both of these as regards complexity of gyres contrast very decidedly with both the fœtal brain given by Bastian (Fig. [113]) and the idiot brain (Fig. [114]) of a patient of Kiernan. The persistency of embryonic features in the gyral arrangement is excellently illustrated in Fig. [115], which represents the brain of an imbecile examined by Spitzka. Here the convolutions in general were few, large, and well marked.[248] The occipital and parietal lobes preponderated in mass as compared with the temporal and frontal. The latter were greatly hollowed out on the orbital face, and the gyri here found were few, simple, and atypical. On the whole the convolutions of the right hemisphere were better marked and the secondary folds more numerous than those of the left hemisphere, and the type of the convolutions presented differences on the two sides. The most pronounced differences were exhibited in the island of Reil and in the occipital lobe. The island of Reil on the left side had fewer and flatter gyri than that of the right side, and resembled in its general aspect the first impression of the brain of an orang-outang. The right island had six folds better marked than those of the left side, but their type was more decidedly radiatory, which was in relation with the unusual shortening of the insular field. The external perpendicular occipital sulcus which Bischoff never found in the adult human brain (but which has been found persistent in a case of imbecility with moral perversion by Sander and in a sane neurotic individual by Meynert) was finely marked upon the right side of the brain under consideration. The fissure was very deep, its posterior wall was slightly bevelled, and covered several secondary gyri of its anterior walls. It differed in position from the similar fissures described by Meynert and Sander in that it did not, as in these cases, unite with the internal perpendicular occipital sulcus and thus simulate the arrangement found in the anthropoid apes. It was merely the unobliterated external occipital fissure of the embryo, and, as in the latter, its medial end if prolonged would have fallen behind the internal perpendicular occipital sulcus. The anomaly consisted therefore in the preservation of an embryonic feature. The arrest of development involved the generally better developed hemisphere. On the left side gyri and sulci were few and simple but typical, the external perpendicular occipital sulcus being interrupted by a broad crossing gyrus. On transverse vertical sections through the hemispheres the average vertical thickness is found to be the same on both sides and normal. The great ganglia were of relatively large dimension, and the white mass of the hemisphere, aside from the internal capsule and the other detachments mediating the connection of the cortex with lower centres, relatively reduced. The caudate nucleus appeared to be of bolder contour on the right side. The right lenticular nucleus presented a larger section area by about 25 per cent. than its fellow of the opposite side. It was much shorter, however, like the insular territory of the same side, and in corresponding sections the posterior end of the left lenticular nucleus was struck while the right was absent. The right nucleus was rounder, the left more triangular in contour in corresponding altitudes. The olivary bodies were asymmetrical, the right one being flatter and smoother than the left. On transverse sections no difference between the olivary nuclei beyond that which occurs in healthy persons could be found; the asymmetry was ascertainably one of prominence only. There was one morphologic appearance noticeable in the fourth layer of the paracentral cortex. This consisted of the presence of round bodies comparable to the nuclei of nerve cells within a thin or no mantle of protoplasm, and presenting every gradation from the free nuclei of the neurolgia, so called, to nerve cells with imperfect processes. These bodies in the human cortex represent imperfectly developed nerve cells and are normally found in the cortex of lower animals. The barren layer or ependyma of the cortex was in places twice as thick in this brain as in the brain of normal beings. This ependyma is the histologic factor of the enormous weight of macrocephalic brains. In a macrocephalic case coming under the observation of Kiernan, of Chicago, in which the brain weighed 68 ounces, the ependyma was five times the normal thickness. The conditions to which Spitzka refers are more or less constantly found in degeneracy. The readiness with which any form of the degenerate series may undergo a metamorphosis into another in the course of hereditary transmission is not, Spitzka remarks, interpretable in any other light than that of the transmission of structure defects either intensified or mitigated in the course of such transmission.

FIG. 111.

FIG. 112.