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 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.[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.
[Illustration: FIG. 111.]
[Illustration: FIG. 112.]
[Illustration: FIG. 113.]
[Illustration: FIG. 114.]
[Illustration: FIG. 115.]
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,[249] 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,[250] 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.
[Illustration: FIG. 116.]
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.
[Illustration: FIG. 117.]
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.[251]