CHAPTER XVI. Degeneracy of the Brain

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, 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 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 (Fig. 112) could not well be greater. Both of these as regards complexity of gyres contrast very decidedly with both the foetal 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. 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.

Transmission of many of these cerebral defects occurs at the moment of conception. The embryonic mechanism of these defects, and the influence which foetal and maternal impressions and injuries exert on the development of the nerve centres, furnish valuable argument by analogy in support of conclusions regarding the degeneracy group. Embryologists imitate known natural teratological states of the nerve centres by artificial methods. By wounding the embryonic and vascular areas of the chick's germ with a cataract needle malformations are induced, varying in intensity and character with the earliness of the injury and its precise extent. More delicate injuries produce less monstrous development. It is particularly the partial varnishing or irregular heating of the egg-shell that results in the production of anomalies comparable to microcephaly and cerebral asymmetry. The constancy of the injurious effect of so apparently slight an impression as the partial varnishing of a structure not directly connected with the embryo at all, suggests a most plausible explanation of maternal and other impressions acting on the germ. The delicate problems in this connection may be inferred from the observations of Dareste that eggs transported in railroad cars, and thus subject to the vibration and repeated shocks of a railroad journey, are checked in development for several days. A less coarse molecular transmission taking place during the maturation of the ovum or its fertilisation, or, finally, during the embryonic stages of the more complex and hence more readily disturbed and distorted human germ, would account for the disastrous effects of insanity, emotional explosions, and mental or physical shocks of either parent on the offspring.

For the majority of cerebral deformities the causes of the deformity must exist in the germ prior to the appearance of the separate organs of the body. Artificial deformities produce analogous results because they imitate original germ defects either by mechanical removal or by some other interference with a special part of the germ. Early involvement of the germ is shown in the fact that the somatic malformation in degeneracy often involves other parts of the body than the nervous axis: defective development of the uro-genital system, deformities in the face, skull, irregularities of the teeth, misshapen ears and limbs.

Those who seek for the source of the arrested or perverted brain development in the reaction of an abnormally growing and ossifying skull on the skull contents are in error. The premature ossification theory does not hold good even for the microcephali; it is to be doubted if it ever had any justification in view of the often open character of the sutures. Taking the well-studied cases of asymmetry, the variability of a single factor shows that caution is needed in referring cerebral anomalies to any single influence. In Muhr's case (cited by Spitzka) the atrophic cerebellar hemisphere was on the same side with the atrophic cerebral hemisphere. The internal carotid artery of that side was of lesser calibre and the entire skull half shortened. Here the lagging behind in growth of one half of the skull appears on first sight to explain the retarded development of the corresponding halves of the cerebrum and cerebellum. In view of the atypy of the gyri, however, an atypy not to be explained purely on mechanical grounds, it is more reasonable to believe that the imperfect development of certain vascular channels was either concomitant or secondary to a primitive anomaly of the cerebral hemisphere. The retarded skull growth would have to be looked upon as a tertiary occurrence and the cerebellar defect as a final ensuing result. Ordinarily with defective development of one cerebral hemisphere the cerebellar defect is on the opposite side, herein following the course of the anatomical connections of that development and of the secondary degenerations. The deviation from this rule in Muhr's case was due to the entering of the abnormal skull-shape, itself secondary to other defects, as an element influencing brain growth at a special period of development. An abnormal shape of the skull, generally associated with a cerebral defect, and hence valuable as a physical sign presumably indicating mental anomalies, may exert an important modifying influence at a late period on the contained brain, but the grosser defects in the cerebral architecture must antedate the period of skull growth and be deeply planted as an original intrinsic fault in the brain blastema itself. The researches of His have shown how important for the definitive shape of the body and its organs are the position of individual cells, the portion of the germ area, the convexity and length of germ curves and the relative rate of growth of different germ areas. And as the experiments of other embryologists have established the possibility of producing monstrosities analogous to cerebral defects by altering the conditions ever so slightly, the general conclusion follows that the fundamental error of development at the foundation of malformations associated with degeneracy is to be located at a very early period of embryonic, or possibly of ovuline life. Certain of these anomalies are due to a disturbance of the balance between the growth of the epiblast and mesoblast derivatives of the brain, others to a disharmony in the development of related associated brain segments; in the severer cases both elements are combined.

It is not difficult to perceive the relation existing between a defective brain weight, paucity of the gyri, deficiency of properly developed cortical cells and such an elementary form of mental aberration as simple imbecility. The subject of the relation between structure and function gains in interest when we leave this domain of simple mental weakness to analyse the relation between structural defects and the positive symptoms of insanity and degeneracy--that is, moral perversion, mental obliquity, delusions, and morbid impulses. Such symptoms are not limited to the higher forms of the degenerate series; they occur, though less constantly and less markedly, in the lower forms.

C. K. Mills, of Philadelphia, on examination of imbecile, paranoiac, and criminal brains, found atypical asymmetry as to gyral and fissure development present. The features of this atypical asymmetry were the existence of a Sylvian fissure shorter on one side than the other, both absolutely and comparatively, and also a more vertical direction of the fissure on one side than on the other, greater exposure of the insula on one side with marked differences in the development of its fissures and gyri, confluence of the central fissure with the Sylvian on one side only, and great tortuosity or bridging of the former fissure in one hemisphere, unusual narrowness, straightness of complication of the precentral or postcentral gyrus on one side; marked difference in the simplicity of complexity of the frontal lobes, great simplicity of the orbital surface on one side, differences in the parietal fissure as to length and interruption, a smaller parietal or marginal or angular gyrus on one side, very great difference in the degrees of confluence and interruption of the fissures in general, exceeding great length vertically of the supertemporal or parallel fissure on one side, unusual differences in the size of the precuneus and cuneus.

A. W. Wilmarth, of Philadelphia, Pa., after a careful study of idiots and imbeciles ranging in intellectual power from the idiot, properly so-called, to the juvenile criminal, paranoiac, and "ne'er-do-well," finds that the brains of these vary greatly along the line pointed out by Spitzka and Mills. One type of brain in this class of children is very simple in its outward configuration. The convolutions are usually coarse, but little convoluted and comparatively free from secondary folds. The fissures tend to assume a confluent type. Another variety, found chiefly among the lowest grades, might well be termed "atypic." A brain without a corpus callosum is a marked example. In the frontal lobe of the right hemisphere the first frontal convolution is quite regular. Below this from the centre of the lobe seven fissures passed in different directions, cutting the tube into a number of radiating convolutions, entirely different from its usual appearance. The short fissure of Sylvius (about three inches in length) passed upward, turned sharply, and passed almost directly behind. Two parallel gyri curved around its posterior extremity. The arrangement of the convolutions of the temporal and parietal lobes were so exceedingly irregular and complex that it was impossible to classify them. In the occipital lobe, on the contrary, the gyri were complete in number and of regular arrangements. In the left hemisphere the arrangement of the frontal convolutions was more regular, but the temporal and parietal lobes presented the same complicated area of surface folding, bearing but little resemblance to the normal brain. The tendency of the convolutions to arrange themselves in parallel curves around the posterior extremity of the fissure of Sylvius was well shown in the brain of a boy of exceedingly low intellect. The frontal lobes in this brain are proportionately large; the convolutions straight, especially the third frontal, the fissures shallow. In the left temporal lobe they are nearly obliterated from pressure of fluid in the ventricles. The ascending frontal convolution on each side appears to be wanting. On the left side a large bridging convolution crosses the middle of the fissure of Rolando. Confluence of fissure is a decided feature of idiot brains. Even where confluence is not complete, the tendency of the principal fissure to cut through separating convolutions is very evident. Were the cases where confluence is nearly complete included, the number would be considerably augmented. The fissure of Sylvius passed into the fissure of Rolando in one case on both sides, in another on one side only. In two other cases they were connected by deep secondary fissures. The interparietalis has its origin in the fissure of Sylvius in four cases on both sides, in five cases on one side only. The calcarine fissure passed completely across the gyrus frontitatus on both sides in two cases, on one side in four cases. In one case the first occipital convolution sank nearly beneath the surface, the next occipital gyrus projecting over it, forming a parietal operculum. There also seems to be a strong tendency to form annectant gyri in the upper part of the parieto-occipital fissure. In no less than six hemispheres of 15 brains were these supplementary gyri found more or less complete. In one case on both sides, in five cases on one side, the parieto-occipital fissure cut through the first occipital convolution into the interparietal fissure. A tendency of the transverse occipital fissure to approach the parieto-occipital fissure is very apparent, though in no case do they coincide. The folds of the cerebral cortex, from a lack of the stimulus of healthy growth, sometimes revert to forms resembling those found in other groups of the animal kingdom.

The fundamental factors of thought and action, as Spitzka terms them, are two: perceptions and motor innervation. These are, in other words, the units of thought and action. They can be properly referred to nerve cell groups as their anatomical seat, and, as far as intellect is in question, to the cell group represented in the more or less diffused and dovetailing areas of specialised function in the cortex cerebri (Fig. 116). But the largest hemisphere known, with the most crowded and most highly developed nerve cells, and the most extensive connections with the periphery, and the most perfect projection of that periphery in its intricately convoluted mass would, functionally speaking, represent nothing but a mass of pigeon-holed impressions stored away without method and without purpose, useless to the organism were it not for those arched fibres uniting the different cortical centres with each other.

These fibre constitute by far the greater part of the white centrum oval of the hemisphere. The total transverse section of the crus and the fibre masses from the thalamus and basilar ganglia, does not comprise more than one-third of the entire mass. In the lower animal this relation is different. The projecting fibres, such as those of crus and capsule and the great ganglia, are not as massive as in man, but they are nearly equal to, and in still lower forms exceed, those connecting the gyri with each other. Hence the chief point of contrast noted on examining a transverse frontal section through the cerebral hemisphere of a man and an ape consists in the mass of the centrum ovale of Vieussens. The whole substance in man actually appears hypertrophied when compared with that of lower animals. It is the associating fibres which mainly mediate that complex co-ordination of the separate units of thought and action which constitute the anatomical basis of the highest mental functions (Fig. 117). The study of the human mind does not resolve itself merely into an analysis of individual faculties such as simple perceptions and motor innervations, but above all requires the establishment of their synthesis into the complex abstractions on which the ego depends.

Neither anatomic nor physiologic researches are calculated to demonstrate just what associating fasciculi or what groups of such fasciculi are subservient to any particular co-ordination. Where, for example, the cortical area for vision overlaps that of the centre for forearm and hand, the associating fasciculus underlying the debatable land is subservient to the co-ordinations employed in writing and drawing. In like manner a similar associating bond extending from the centre of auditory word symbols to that of the tongue and lip centres may be considered a chief factor mediating the speech co-ordinations. A child originally has no adequate notion of distance or perspective, but will, in the first week of life, grasp at objects fifty feet away. Its first ideas of space are gathered from its own skin sensations; it learns to distinguish between single impressions when touching foreign bodies, and associated double ones as when it touches a part of its own body. In great part this may even be accomplished by an active infant during the last months of utero-gestation; it has learned thus to separate the conception of its own body from the confused chaos which all impressions originally constitute to the infant; the next lesson is to learn that to reach certain objects it moves a certain distance, while others are immediately in reach. It then discovers, therefore, that the discrimination by the eye is possible, since intervening objects which it has learned to measure by its own body or bodily movements as a gauge permit an approximate judgment of distance, in aid of which comes experiment in the shape of time requirements, since to go so far requires such time, while to go further requires a much greater. The crude ideas of space at this time must involve areas in the cortex devoted to motion and to general sensation situated in the Rolandic region. Those devoted to visual impressions are largely situated in the occipital region, and those devoted to time may be located in the frontal lobes. Further analysis of the more elaborate sense of space possessed by adults, involving the play of equilibrium and the appreciation of movement and direction in foreign objects, shows that cortical areas situated in nearly every part of the hemispheres are subsidiary to it and connected by fibre tracts of different lengths and courses. It is evident, therefore, that the mal-connection of cortical centres is at the root of various tropho-neurotic, nervous, mental, moral and other perversions exhibited in degenerates. Deformity and deficiency of the corpus callosum in some degenerates is but an expression of general defect of associating tracts. Convolutional aberration in others is but an expression of imperfect development of end stations and fibre systems. All mental and moral disturbances are associated with perversions of the functions of the cerebral hemisphere, but the converse, that cerebral hemisphere lesions only are the essential accompaniments of mental symptoms evinced during life, is not true. Lesions of the pons, the crura, and thalami are accompanied by more or less complete obliteration of consciousness, blurring of the perception, confusion in the intellectual sphere, even where the lesion is not of such a character as to disturb the neighbouring ganglia by pressure. Two explanations are possible of this phenomenon. Either the vaso-motor centre for the cortical vessels is under the control of isthmus ganglia partially, and hence isthmus lesions by irritation or destruction of the centre excite or paralyse the vascular tubes of certain cortical districts, or pathologic interruption of the great nerve tracts involves functional disturbance of cortical end stations. The first explanation is applicable in cases where general and widespread disturbance, somnolence, excitement, or depression are found. The latter where the disturbance is partial in character. If all avenues of sensory perception be closed unconsciousness in the way of sleep speedily follows. Interruption of the perception tracts is followed by corresponding phenomena, though less extensive when occurring in the isthmus territory. That an irritative lesion in the line of the centripetal tracts can influence cortical life is shown by thalamus lesions in which hallucinations are sometimes present. Here the cause of the hallucinations is in the lower centre, but the entry of these into the intellectual sphere can take place only in the cortical termination of that tract, since at this point only through the connecting associating tracts can it become a part of the ego.

Meynert traced an enormous division of the crus directly to the frontal lobe and the lenticular nucleus, and showed that this portion through the transverse fibres of the pons was of necessity connected with the cerebellum, and that far other functions are to be located in the cortex than merely muscular innervation, visual and auditory perceptions. The restiform columns derived from spinal fibres enter the cerebellum and terminate chiefly in its hemispheres. The cortex of these hemispheres is connected by radiatory fibres, with the dentated nucleus, which is a recipient of fibres of the auditory nerve. The cortex of the cerebellar hemisphere receives fibres both from the sensorial periphery of the body and the semicircular canals. From this reception area the transverse fibres of the pons originate and enter the crus. It is these which enter the frontal lobe and lenticular nucleus. In no respect does man so much differ from the ape as in the quantitative development of these fasciculi. Their development is intimately associated with the mass of the frontal lobe, and there is every reason for considering them the channel of information of the equilibrium and possibly of the senses of space and time, on which the scope of the mind is so closely dependent. Lesions in these tracts may disturb these sensations, and the entire mental architecture may totter with the withdrawal or weakening of so important pillars. The congenital asymmetry of the peduncular tracts observed in certain cases of mental and moral perversion are not without bearing on the symptoms of those cases. And this explanation would be adjunct to the principle of mal-development of the associating tracts here advanced in explanation of other symptoms of these same states. It is a logical truism that complex cerebral functions have a complex substratum. Nothing could be more unphilosophical, for example, than to speak of "intellectual cells" (Denkzellen) in the cerebral cortex. Simple elements can have but simple functions; complex functions require a union of numerous simpler elements in a complex structural combination.

Such symptoms as epileptic explosions are admittedly connected with no demonstrable anatomical aberration, and yet when epileptic explosions of a certain type are found associated with a cortical lesion they are to be regarded as symptoms of that lesion. Morbid projects, delusions, and moral perversion are simply functional perversions of a properly built cerebral mechanism or the outcome of a visible structural defect. And when the latter is palpably attributable to an error in development and occurs with a certain constancy in similar cases, a fundamental relation must be assumed between the defect and the general tenor of the symptoms.

There is a great difference clinically between the effect of congenital and acquired lesions. When porencephaly (a deformity originally studied by Heschl) dates from infantile or foetal life, imbecility is always present during life; but where it is developed in the matured brain imbecility does not necessarily result.

Deficiencies in the cerebral vascular system underlie the pathological phenomena on the basis of infantile cerebral paralysis, and allied hereditary and congenital states. The degenerate conditions in the spinal cord are essentially those described by Spitzka as occurring in the brain. Vascular states, either as to irregularities in the number of vessels or in the vessels themselves, underlie, as in the case of the cerebral palsies, hereditary ataxias and other congenital and hereditary spinal cord disorders.