HEREDITY AND ATAVISM
Heredity, like other biologic factors, starts with the cell. As elsewhere
pointed out, reproduction is first unicellular in type and involves an
expenditure of nutritive force antagonistic to the growth of the cell. As
Geddes remarks,[66] no one can dispute that the nutritive, vegetative, or
self-regarding processes within the plant or animal are as opposed to the
reproductive, multiplying, species-regarding processes, as income to
expenditure or as building up to breaking down. But within the ordinary
nutritive or vegetative functions of the body there is necessarily a
continuous antithesis between two tissue-changing sets of processes,
constructive and destructive metabolism. The contrast between these two
processes is seen throughout nature, whether in the alternating phases of
cell-life or in the great antithesis of growth and reproduction.
The starfish, deprived of an arm, replaces this by a fresh growth; crabs
can renew the great claws which they have lost in fighting; even as high
up as the lizard the loss of a leg or a tail can be made good. In a great
variety of cases a kind of physiological forgiveness is shown in the
reparation of even serious injuries. Now this "regeneration," as it is
called, is a process of reproduction. By continuous growth the cells of a
persistent stump are able to reproduce the entire number. A sponge, a
hydra or a sea-anemone may be cut into pieces with the result that each
fragment grows into a new organism. The same is done with many plants; and
though the division is artificial the result shows how very far from
unique is the process spoken of as reproduction, which is but more or less
discontinuous growth. This is well shown in the evolution onward
insensibly from cases of continuous budding, as in sponge or rosebush, to
discontinuous budding in hydra zoophyte and tiger-lily, where the
offspring vegetatively produced are sooner or later set free.
The enormous expenditure of force required for unicellular reproduction is
lessened by conjugation with another cell through satisfaction of cell
hunger; and this, by making two cells do the work of one, lessens the
amount of nutritive force expended by each. Evolution in fertilisation has
the following steps:--
I. Formation of plasmodia.
II. Multiple conjugation.
III. Conjugation of the two similar cells.
IV. Union of incipiently dimorphic (different) cells.
V. Fertilisation of differentiated sex elements.
As Maupas has shown, by the time conjugation of two similar cells is
reached, the paranucleus in both is incipiently hermaphroditic. The
impelling force leading to conjugation is, as Rolph has shown, cell
hunger. Conjugation, he remarks, is a necessity for satisfaction, a
gnawing hunger which drives the animal to engulf its neighbour, to
isophagy (self-eating). The process of conjugation is only a special form
of nutrition which occurs because of a reduction of the nutritive income
or an increase of the nutritive needs. It is an "isophagy" which occurs in
place of "heterophagy" (eating of others). "The less nutritive, and
therefore smaller, hungrier, and more mobile organism is the male, the
more nutritive and usually relatively more quiescent organism the female.
Therefore, too, is it that the small starving male seeks out the large,
well-nourished female for purpose of conjugation, to which the latter, the
larger and better nourished, is on its own motive less inclined." The
unicellular type of reproduction long remains after sex differentiation
has occurred and assumes the form of parthenogenesis (virgin generation).
The phenomena of this demonstrate that the female element is the highest
in evolution. Spitzka[67] has shown that the ovum possesses an inherent
activity independently of fructification. How far this may extend in the
direction of more mature development is shown by what is known about
parthenogenesis. This is the development of living beings without a
father. Bees, some butterflies, ants and wasps notoriously multiply their
kind without sexual congress. As a rule the parthenogenetic offspring are
themselves incapable of further procreating their kind. But to this there
are remarkable exceptions. The aphides multiply for many generations
without the intervention of a male. Weigenbergh has shown that the
silk-moth can be propagated as long as the male element is permitted to
act at every fourth generation. The _Artemsia salina_, a minute
crustacean living in saline springs, reproduces its kind for years
without a male being present, males being produced at definite intervals
only (Von Siebold). Among the vertebrata parthenogenetic development has
also been observed, though rarely reaching maturity. Thus, segmentation
occurs in unfertilised ova of the chicken (Oellacher), of the fish
(Burnett and Agassiz), and of frogs (Moquia-Tanden). Spitzka has seen a
blastoderm form in unfertilised ova of the toad-fish (_Batrachus tau_).
Hensen isolated the oviducts of a rabbit, thus rendering the admission of
semen impossible, while the ova, discharged at heat, were compelled to
remain in these oviducts. Three years later he killed the animal and found
the ova had developed into twisted, club-shaped, hollow sacs. The
development in the female ovary (also, though very rarely, in the male
testicle and parotid gland, which show such a remarkable metastatic
sympathy in mumps), of dermoid cysts (containing bones recognisable as
maxillaries with teeth, hair, and skin, rudimentary bowel, gland, and
brain traces), even in undoubted virgins, proves that even the human ovum
is capable of parthenogenetic development. While such development, so far
as known to science, is always abortive, and while, as Washington Irving
remarks, the ingenious maiden who to-day would attribute conception to any
other cause than sexual congress would find it difficult to overcome the
prejudice of scientists, yet embryology, while declaring immaculate
generation improbable, does not pronounce it impossible. A worker bee may
be an offspring of an unimpregnated queen bee. What is a regular
occurrence in one class of animals is sometimes observed as an
exceptional one in another class. If the startling and apparently
miraculous nature of a virgin generation of a living child be regarded as
the sole objection to receiving such a fact, its defender might urge that
the virgin generation of a dermoid cyst with all the traces, however
aborted, of vertebrate organisation, is only a shade less startling and
miraculous.
This power of parthenogenesis, however, cannot continue indefinitely
without extinction. This has been shown by the careful experiments of
Maupas, who had observed 215 generations of an infusorian without sexual
union. He found that then the family became extinct. Powers of nutrition,
division, and conjugation with unrelated forms come to a standstill. The
first symptom of this senile degeneration is decrease in size, which may
go on till the individuals only measure a quarter of their normal
proportions. Various internal structures then follow suit "until at last
formless abortions occur, incapable of living and reproducing themselves."
The nuclear changes are no less momentous. The important paranucleus is
fatally sterile. The larger nucleus may also become affected, "the
chromatin gradually disappears altogether." Physiologically, too, the
organisms become manifestly weaker, though there is excessive sexual
excitation. Such senile decay of the individuals and of the isolated
family inevitably ends in death. Sexual union in those infusorians,
dangerous perhaps for the individual life, a loss of time so far as
immediate multiplication is concerned, is, in a new sense, necessary for
the species. The life runs in cycles of a sexual division which are
strictly limited. Conjugation with unrelated forms must occur else the
whole life ebbs. Without it the protozoa, which some have called
"immortal," die a natural death. Conjugation is the necessary condition of
their eternal youth and immortality.
Starting from this standpoint the relative functions of the two sexes in
heredity are apparent. The original function of reproduction, that of cell
division, is the part of the female. The male in the lower instances
simply supplies the female with nutriment. Thus in certain plants there is
nothing but a subtle osmosis between the sexes. This is also the case with
some of the lower infusoria. With a rise in evolution protoplasm becomes
differentiated. At the outset of the subject of heredity it is evident,
therefore, that the female furnishes the type which is best capable of
development when properly nourished by a highly developed male. To
deficiencies in both particulars are due defects and variations in the
offspring. As the product of fructification is longest under the nutritive
control of the female, her influence is most emphatic in either redeeming
defects or producing them. Heredity, according to Ribot, Spitzka, Fere,
and others, is divisible into direct heredity, indirect heredity, and,
more dubiously, telegony. Direct heredity consists in the transmission of
paternal and maternal qualities to the children. This form of heredity has
two aspects: (1) The child takes after father and mother equally as
regards both physical and moral characters, a case strictly speaking of
very rare occurrence; or (2) the child, while taking after both parents,
more especially resembles one of them. Here again distinction must be made
between two cases. The first of these is when the heredity takes place in
the same sex from father to son, from mother to daughter. The other which
occurs more frequently, is where heredity occurs between different
sexes--from father to daughter or from mother to son. Reversional heredity
or atavism consists in the reproduction in the descendants of the moral or
physical qualities of their ancestors. It occurs frequently between
grandfather and grandson, as well as between grandmother and
granddaughter. Collateral or indirect heredity, which is of rarer
occurrence than the foregoing, and is simply a form of atavism, subsists,
as indicated by the name, between individuals and their ancestors in the
indirect line--uncle, or grand-uncle and nephew, aunt and niece. Finally
(3) there is telegony, or the heredity of influence, very rare from the
physiological point of view, which consists in reproduction in the
children by a second marriage of some peculiarity belonging to a former
spouse.
In dealing with heredity the position of Weismann and others, that
acquired characters cannot be inherited, needs a short examination. In his
later work Weismann has practically abandoned the essential basis of his
position by admitting that maternal nutrition may play a part in
determining variation. He[68] now asserts that the origin of a variation
is equally independent of selection and amphimixis, and is due to the
constant occurrence of slight inequalities of nutrition in the germ plasm.
As acquired characters affecting the constitution of the parents are
certain to affect the nutrition of the germ plasm, it is therefore
obvious, according to Weismann's admission, that acquired characters or
their consequences will be inherited. This is an emphatic though
concealed abandonment of the central position of Weismann.
One of the stock arguments of the Weismann school is drawn from results of
the Jewish rite of circumcision. While the operation is not calculated to
make a profound impression on the constitution, and furthermore, as being
performed on the male, less likely to affect the race, still the alleged
non-inheritance of its results is much over-estimated. William Wolf,[69]
of Baltimore, Maryland, who has circumcised six hundred Jewish children,
finds on careful examination, that 2 per cent. were born partially
circumcised and 6 per cent. were born with a short prepuce. P. C.
Remondino,[70] of Los Angeles, California, has seen a large number of
cases of absence of the prepuce which proved to be hereditary. After a
confinement his attention was once called to the child by the nurse, who
thought it was deformed. The nurse was astonished at the size and
appearance of the glans penis. On examination the prepuce was found to be
completely absent. On inquiry, the father and another son, born more than
twenty years previously (comprising every male member of the family), were
found to have been born with the glands fully exposed. He has seen a
French family similarly affected.
Similar, but much stronger, results have been obtained by me through the
courtesy of the Reverend Drs. S. Bauer, M. A. Cohen, and B. Gordon, all of
Chicago. Dr. Bauer, who has been seventeen years in the practice of the
religious rite of circumcision, has circumcised 3,400 boys and has found
preputial absence in about 3-1/2 per cent. of the cases. Dr. Cohen, who
has been two decades in the practice, has performed 10,000 circumcisions.
He has found the prepuce wanting in 500 cases; partially developed in 300
cases; slightly developed in 2,000 cases. Dr. Gordon has performed 4,400
circumcisions in twenty-five years. He has found the prepuce absent in 15
cases; partly wanting in 200, and slightly developed in 2,200 cases.
These, it should be remembered, are only cases where preputial change
forced itself on the observer, who was not pursuing investigations on this
point.
The volume of Hebrew casuistic religious literature collected in the
Medrash, evidences as I have elsewhere[71] shown the frequency of
congenital preputial defect.
That acquired characters can be transmitted has been definitely shown by
the experiments of George Roe Lockwood,[72] of New York, anent hereditary
transmission of mutilations. White mice were selected, as they begin to
breed when thirty days old, and breed every thirty days. He bred in-and-in
for thirty-six generations, destroying the weakly, and thus obtained finer
animals than the first pair. He selected a pair, caged them by themselves,
and clipped the tails of the young. When they were old enough to breed, he
selected a pair and clipped the tails of their progeny. In the seventh
generation he obtained some tailless mice, and finally a tailless breed.
The experiments have one possible element of error; white mice, like all
albinoes, are a degenerate type. At the same time these experiments show
that accidental mutilations favoured by circumstances are inherited.
Eimer[73] reports the case of a pair of long-tailed pointers which had
once produced a litter of long-tailed pups. In order to obtain
short-tailed pups the owner had the tails of both shortened. The bitch
from that time produced repeatedly short-tailed pups only. As the most
careful attention was paid to the parents, no error can be suspected in
this case, which, moreover, excites no surprise among dog-breeders.
Brown-Sequard[74] has shown that a peculiar alteration of the shape of the
ear or a partial closing of the eyelids is inherited by the offspring of
animals in which these changes were caused by dividing the sympathetic.
Exophthalmia (eye protrusion) was inherited by guinea-pigs in whose
parents this protrusion of the eyes had occurred after an injury to the
spinal cord, and so were bruises and dry gangrene, as well as other
trophic disturbances in the ear, due in the parents to an injury to the
restiform body of the brain. Loss of certain phalanges or of whole toes of
the hind feet which had occurred in the parents in consequence of division
of the sciatic nerve was inherited. Diseased conditions of the sciatic
nerve occurred in the offspring of guinea-pigs in which this nerve was
divided. Forty guinea-pigs in which one or both eyes showed more or less
morbid change were descended from three individuals in which one eye had
become diseased in consequence of transverse section of the restiform
body. Twenty guinea-pigs exhibited muscular atrophy on the upper and lower
sides of the thigh, when in the parents such atrophy had been caused by
section of the sciatic nerve.
The experiments of Brown-Sequard, Westphal, Dupuy[75] and Obersteiner,
which show that artificially induced epilepsy is inherited, still further
bear out the conclusions resultant on the inheritance of these
mutilations. Indeed, Weismann has been forced to that _reductio ad
absurdum_ in science, narrowly limited definitions, in order to maintain
his position. "But although I hold it improbable," he remarks, "that
individual variability can depend on a direct action of external
influences upon the germ cells and their contained germ plasm, because, as
follows from sundry facts, the molecular structure of the germ plasm must
be very difficult to change, yet it is by no means to be implied that this
structure may not possibly be altered by influences of the same kind
continuing for a very long time. This much may be maintained: that
influences which are mostly of variable nature, tending now in one
direction, now in another, can hardly produce a change in the structure of
the germ plasm, and this is the reason why the cause of inheritable
individual differences must be sought elsewhere than in these varying
influences." "No one has doubted," he says, in reply to objections made by
Virchow, "that there are a number of congenital deformities, birth-marks,
and other individual peculiarities which are inherited. But these are
acquired characters in the above sense. True, they must once have appeared
for the first time, but we cannot say exactly from what causes; we only
know that at least a great proportion of them proceed from the germ
itself, and must therefore be due to alterations of the germinal
substance. If Virchow could show that any single one of these hereditary
deformities had its origin in the action of some external cause upon the
already formed body (soma) of the individual and not upon the germ cell,
then the inheritance of acquired characters would be proved. But this no
one has yet succeeded in proving, often as it has been maintained."
The crucial test which Weismann demands is furnished by Dupuy,[76] who
made one thousand experiments on guinea-pigs to the fifth generation,
critically rejecting all results which did not correspond to the most
rigid tests of direct heredity, excluding all instances of indirect
heredity, however demonstrable. He found that certain lesions of the
spinal cord, or the brain or the sciatic nerve, give rise in guinea-pigs
to epilepsy.
In from three to six weeks after the operation an alteration in the
nutrition takes place in an area of skin which is limited by a line
starting from the outer canthus of the eye, and running to the median line
on the upper lip, enclosing the nostril, thence backward enclosing the
lower jaw, to the anterior portion of the shoulder to the median dorsal
line, to the base of the ear and inner canthus of the eye. The alteration
in nutrition occurs on the side corresponding to the injury. The pain,
heat and cold sense disappear by degrees, while touch appears to be
exalted. Very soon, tickling this zone of skin gives rise to twitchings
limited to the muscles of the eye and the eyelids on the same side. Later,
the muscles of the mouth and of the face are affected, still later the
contractions become more general, until the whole side is the seat of
convulsions, then the convulsions attack the other side also. When things
have come to this point the convulsions precede by a very short time
complete loss of consciousness. If the subject of experiment be white, it
is found that there is paleness of the face, but in all cases there is
little foam at the mouth and dilatation of the pupils. The animal
sometimes utters a cry corresponding to the epileptic cry in the man. Not
only are the convulsions identical with those in epileptic man, but there
is also loss of consciousness, a state of torpor, stupor, and even
sometimes insanity. When epilepsy is due to the destruction of the sciatic
nerve, the foot of the affected side loses the two outer toes, so that the
animal has only one toe, the inner. When young are born to such a parent
or parents (for it matters not whether one or both of the parents have
been operated upon), they have very often only one toe on the posterior
foot. Sometimes, however, they have additional toes, which, in this case,
are attached by a pedicle to the limb.
Those peculiarities observed in the parents are in all their details
witnessed in the guinea-pigs hereditarily born toeless, who have developed
epileptic phenomena. In Dupuy's cases not only is the epileptic tendency
(of which Weismann gives a wholly imaginative microbic explanation)
inherited, but the very stigmata (loss of toes) which mark development of
the parental epilepsy.
E. D. Cope's[77] careful studies of the effects of impacts and strains on
the feet of mammals are testimony difficult for Weismann to explain, since
they also meet his requirements.
Weismann's admission of the inheritance of a tuberculous habit must
logically, from the standpoint of degeneracy, be regarded as destroying
his claims.
Kiernan has observed the case of a female cat in which brain mutilation
had been induced to secure secondary cerebro-spinal degenerations. The
mutilations were made under antiseptic precautions. The descendants of
this cat had traces of the mutilation, and its results until the fourth
generation, when the breed became extinct. This instance certainly fulfils
all Weismann requirements.
In the Lambert family a skin deformity, the last result of degeneracy in
previous generations, was transmitted. This peculiarity appeared first,
according to Proctor,[78] in the person of Edward Lambert, whose whole
body, except his face, the palms of the hands and the soles of the feet,
was covered with a horny excrescence. He was the father of six children,
all of whom as soon as they had reached the age of six weeks presented the
same peculiarity. The only one of them who lived transmitted the
peculiarity to all his sons. For five generations all the male members of
the family were distinguished by the horny excrescence which had adorned
the body of Edward Lambert.
Shwe-Maong, one of the hairless Burmese, when thirty years old had his
whole body covered with silky hairs, which attained a length of nearly
five inches on the shoulders and spine. He had four daughters, but only
one of them resembled him. She had a son who was hairy like his
grandfather. The case of this family illustrates rather curiously the
relation between the hair and teeth; for Shwe-Maong retained his milk
teeth till he was twenty (when he attained puberty); then they were
replaced by nine teeth only, five in the upper and four in the lower jaw.
Eight of these were incisors, the ninth (in the upper jaw) being a cuspid
tooth.
Certain motor expressions of disturbed functions are also inherited.
Galton describes the case of a man who, when he lay fast asleep on his
back in bed, had the curious trick of raising his right arm slowly in
front of his face, up to his forehead, and then dropping it with a jerk,
so that the wrist fell heavily on the bridge of his nose. The trick did
not occur every night, but occasionally, and was independent of any
ascertained cause. Sometimes it was repeated incessantly for an hour or
more. The gentleman's nose was prominent and its bridge often became sore
from blows which it received. At one time an awkward sore was produced
that was long in healing on account of the recurrence, night after night,
of the blows which first caused it. His wife had to remove the buttons
from the wrist of his nightgown, as it made severe scratches, and some
means were attempted of tying his arm. Many years after his death his son
married a lady who had never heard of the family incident. She, however,
observed precisely the same peculiarity in her husband; but his nose, from
not being particularly prominent, has never as yet suffered from the
blows. The trick does not occur when he is half asleep, as, for example,
when he is dozing in his armchair, but the moment he is fast asleep he is
apt to begin. It, as with his father, is intermittent, sometimes ceasing
for many nights, and sometimes almost incessant during a part of every
night. It is performed, as it was with his father, with his right hand.
One of his children, a girl, has inherited the same trick. She performs it
likewise with the right hand but in a slightly modified form; for after
raising the arm she does not allow the wrist to drop upon the bridge of
the nose, but the palm of her half-closed hand falls over and down the
nose, striking it rather rapidly, a decided improvement on the father's
and grandfather's method. The trick is intermittent in the girl's case
also, sometimes not occurring for periods of several months, but sometimes
almost incessantly. These "tricks" suggest nocturnal epilepsy, however.
The face of a child is often fully developed, yet, owing to some of the
constitutional diseases, arrested development of the face at this point
takes place. The second generation inherits this deformity, while the
grandparents possess normally developed faces.
The following case came under my own immediate observation. The
grandfather was in the habit of sitting in front of the fire with fingers
locked together twirling the thumbs in one direction, and then
occasionally knocking the thumb nails together. Two of his three sons
inherited this habit; the third brother had the habit of biting his nails
when in a fit of abstraction. The nephew of the last has a similar habit
under the like conditions. The children of this nephew have in two
instances shown a tendency to pick at the nails when in an unconscious
state, from acute disease. The third child has a periodical tendency to do
the same since it was four months old.
V. P. Gibney,[79] of New York, has reported a family consisting of father
and mother, five children, and one grandchild. The father and mother are
semi-ambidextrous. All of the children and the grandchild are
semi-ambidextrous to an annoying degree; all of the movements which they
perform with one hand are simultaneously performed by the other hand. The
girls are obliged to use only one hand when dressing themselves, or when
cutting patterns, and hold the other hand down by their side, because the
two hands perform the same movements at the same time and would interfere
with each other.
One factor in heredity concerning which there has been much dispute, and
whose existence has been denied because of certain theories anent the
nerve connection of the mother and foetus, is that of maternal
impressions. As Fere[80] has shown, the foetus exhibits very decided
reaction to sensory impressions on the mother. He cites cases of several
women who, often in the midst of an ordinary dream, producing but very
moderate excitation, not generally interrupting sleep, were awakened by
foetal movements. The dreams had nothing of the nightmare which would
cause sudden contraction under the influence of a terrifying idea. They
were merely the ordinary phenomena of sleep. Mental changes of the mother
hence excite motor reactions in the foetus, and, as with sensorial
excitations, these reactions are stronger in the foetus than in the
mother. The mechanism of these motor reactions is, Fere points out,
obviously due to unconscious and involuntary movement of the muscle walls
of the womb. The organisation of a morbid predisposition may be largely
influenced by an accident accompanying conception or gestation. In some
degenerates cannot be found a trace of hereditary defect. The fact cited
explains how sensorial excitations or repeated and violent emotions in the
mother during pregnancy give rise to profound nutritive troubles in the
foetus, and especially in its nervous system. These congenitally
degenerated beings (_ab utero_) can hardly be distinguished from those
having direct heredity. A considerable number of cases of epilepsy,
idiocy, &c., are recognised as having arisen from alcoholism in the
mother. Psychic troubles in the mother may react upon the foetus in an
analogous way. The prominent facts which show the influence of the psychic
state of the mother upon the somatic condition of the foetus explain the
action of the imagination of the mother upon the development of the
product of conception. The opinion which refers the origin of birth-marks
to intense mental impressions on the part of the mother is not without
physiological foundation. Concurrently with the motor phenomena,
stigmata[81] may become developed by vascular and nutritive troubles
produced under the influence of a strong excitation or by the imagination.
Spitzka,[82] who approached maternal impressions from an actively
sceptical standpoint, had his scepticism shaken by specimens (preserved in
the British Museum) of newly hatched chicks, all of which had a curved
beak like a parrot, and the toes set back as in that bird. According to
the report of the curator the hens in the farmyard where these
monstrosities were hatched had been frightened by a parrot which, having
escaped, fluttered among them some time before the eggs were laid and
greatly frightened those from whom the malformed chicks were received. It
is certain that the chief argument of those who deny that maternal
impressions are transmitted is defeated by this case. They have usually
asserted that the explanation of the nature and cause of a birth-mark was
always an after-thought on the part of the mother. But there was no
after-thought in this case. The hens did not publish a theory as to the
malformation of their chicks. It was their owner, a gentleman of
intelligence and culture, who observed the casual occurrence, and who
verified the almost photographic truthfulness of the germ monstrosity by
depositing it in a museum as a permanent record at which none may cavil.
Since then, the singular freaks attributable to maternal impressions of
women, seen by Spitzka, have become so numerous that he has been compelled
to negative the argument that they were merely accidental coincidences. He
has never seen an idiotic, malformed child or one afflicted with morbid
impulses derived from healthy parents free from hereditary taint in which
a maternal impression could not be traced.
In a large number a direct correspondence between the maternal impression
and the nature of the deformity or peculiarity could be discovered. He
reports the case of a woman, about five months pregnant, who, while
standing in her yard, saw her husband stab into the belly of a goat he had
slaughtered. The sight of the suddenly protruding visceral mass, which
happened to be imperfectly bilobar, shocked her extremely, and, starting
back, she, in her great revulsion, feeling a strange sensation at the nape
of the neck or back of the head, clutched the former with her right hand.
The impression continued to haunt her. When the child was born and she
saw its deformity she instantly exclaimed, "Oh, the intestines of that
goat!" At the back of its head the child had a large tumour of the
consistency of a loose sac of a bluish colour, showing convolutions
interpreted by the mother as a reproduction of the intestinal convolutions
that had so shocked her. In reality they were the convolutions of a hernia
containing the posterior ends of both cerebral hemispheres. The accidental
resemblance of the deformity to the mental impressions was striking.
A. Lagorio[83] brought before the Chicago Medical Society several cases in
which maternal impressions had produced decidedly abnormal births with
deformities resembling those feared by the mother. Kiernan, in discussing
these, pointed out that all were instances of checked development. He was
of opinion that moral shock, generally directed, played the chief part in
maternal impressions through checking development and causing either
general or local reversion. Here, as Spitzka[84] shows, the statistical
method can be applied. It has been long known that profound grief, mental
or physical shock acting on the mother, produce cerebral defect or
generally arrested development in the offspring. Of 92 children born in
Paris during the great siege, 1870-71, 64 had mental or physical anomalies
and the remaining 28 were weakly, 21 were intellectually defective
(imbecile or idiotic), and 8 showed moral or emotional insanity. These
figures, furnished by Legrand du Saulle, justify the popular designation
by the working men of Paris of the defective children born in 1871 as
"_enfants du siege_."
After the great Chicago fire in 1871 birth-marks, deformities, and mental
defects were noticed to occur among the offspring whose mothers were
pregnant with them pending the exciting time during and after the
conflagration.
Spitzka has seen in practice, constitutionally melancholic or mentally
defective children in whom no other predisposing cause could be discovered
than that the mother was struggling with direct or indirect results of the
financial crisis of 1873. In several of these cases the death of the
father was a contributory cause of maternal depression. In Berlin the
financial crisis of 1875-80 was followed by an increase in the number of
idiots born. Lombroso attributes a series of cases of microcephaly to
profound mental impressions occurring during pregnancy. To the same class
of cases belong the hermaphrodites born by mothers who have been
frightened in their first pregnancy and who continue to bear
hermaphrodites. The continual and not ill-founded dread that the
succeeding children may resemble the first is to be regarded as a
contributory cause. Observers who have had a large experience with
illegitimate births believe that the mental agony suffered by the
unfortunate mother reacts upon the foetus, causing arrest of development,
and thus accounting for the frequent occurrence of idiocy in illegitimate
children.
The influence of maternal diet on the foetus is excellently illustrated in
the results of the "fruit diet" advised by certain vegetarians. Here the
children[85] become, as Elise Berwig has recently shown, rickety,
irritable, peevish, liable to convulsions, morally peculiar, and otherwise
defective in contrast with children born of the same parents without
"fruit diet" during pregnancy.
Kiernan,[86] after citing instances reported by Amabile, Carson, F. B.
Earle, Erlenmeyer, F. H. Hubbard, C. H. Hughes, Mattison, and others, of
congenital opium habit where opium was needed to preserve the infant
during the first months of life, states that inheritance of the opium
habit seems at first an isolated phenomenon, but zoologists have pointed
out that pigeons whose ancestors were fed on poppies became intractable to
opium. Murrell found that the same was relatively true in England of
persons descended from Bedfordshire ancestors who used infusions of
poppies as a prophylactic against malaria. Nervous diseases were, however,
relatively prevalent in these districts. Narcotic habits in the ancestors
produces descendants in whom the normal checks on excessive nervous action
are removed, so that paranoiacs, periodical lunatics, epileptics,
hysterics, congenital criminals, congenital paupers, or other degenerates
result. This influence is most strongly exerted when the maternal ancestor
is the one affected, for to her is committed the development of the ovum
prior to conception and of the child subsequently. If either is interfered
with by a habit, a being defective in some respects is the result. The
direct inheritance of the opium habit has been shown experimentally by
Levenstein, who found by experiments on pregnant dogs and rabbits that the
use of opium during pregnancy produced either abortion or still-births, or
rapidly dying offspring.
In a similar manner Rennert[87] has shown that lead-poisoning occurring in
the mother is apt to produce macrocephalism with frequent idiocy in the
child.
This brings the observer face to face with the problem of morbid heredity.
It may at once be admitted that, as has been claimed by a large number of
observers, morbid heredity, especially in its graver forms, is much less
frequent than at first would be expected. J. P. Gray, of Utica, New York,
went so far as to claim that disease is never transmitted, but this is
contradicted by his own hospital reports, which, to the day of his death,
contained a table headed, "Statistics of hereditary transmission of the
disease." It is true, however, that the descendants of a victim of
morbidity or abnormality do not always exhibit the morbidity or
abnormality of the ancestor. In some cases all apparent morbidity or
abnormality is wanting. In other cases slighter abnormalities are to be
detected. Here the observer is brought face to face with the operation of
two general principles which are interdependent: the transmutation of
heredity and atavism, or "throwing back" as the cattle breeders call it.
Tennyson voices the general erroneous opinion of the always evil effects
of atavism in his "Locksley Hall Sixty Years After":--
"Evolution ever climbing after some ideal good
And Reversion ever dragging Evolution in the mud."
As Kiernan has shown, atavism at times tends to preserve the type, and
offsets the influence of degeneracy. This element of atavism underlies not
merely the production of the sound scions of degenerate stock, but also
those in whom the degeneracy affects the earlier and not the later
acquirements of the race. The contrast of the moral imbecile who is unable
to acquire an idea of right, or the idiot of the lowest grade who can
hardly be taught to keep himself clean, with the otherwise sound, sane,
able victim of hereditary gout, is very great. Yet all the links of the
chain connecting, in the same family, these contrasted types, can often be
found. The law laid down as to absolute extinction through degeneracy by
Morel and others can only be regarded as absolutely true when applied to a
given type rather than the race as a whole. Indeed, environment may play a
part in preserving a degenerate who would otherwise die out. Thus in
societies at a certain stage of culture imbeciles, paupers, lunatics, and
congenital criminals live at large and even propagate through legal
marriage. The seemingly enormous increase of the defective class which
occurs in frontier communities when the classes begin to be placed in
public institutions is an excellent illustration of this.
Manifestations of morbid heredity result not in inheritance of the whole
defect but in disturbance of relations of structure and hence of function,
producing, as Kiernan remarks, a constitutional deficiency which takes the
line of least resistance. The extent and direction of this line of least
resistance depend on the amount of healthy atavism which separate organs
and structures of the body preserve. The line of least resistance
sometimes taken is excellently illustrated in the occurrence of stigmata
already pointed out in the case of epileptic guinea-pigs.
This unilateral predisposition (which, as Kiernan has shown, is due
usually to heredity or intra-uterine causes) may be artificially
produced. Kasparek[88] cut one sciatic nerve of a guinea-pig and (after
all inflammatory symptoms had subsided) injected the opposite ear with
cultures of pus microbes. He killed the animal after some days. The sound
side was found free from suppuration, but immense abscesses existed on the
side of the cut nerve. Such local predisposition was pointed out by
Merrill[89] over forty years ago. This condition occurs, as Fere has
shown,[90] in many systemic and infectious diseases which presents a
localisation due to heredity, or determined by anterior morbid state of
the nervous symptom. Sometimes these manifestations are limited to the
side free from nervous trouble.
As a rule they attack the side which is the predominant seat of nervous
symptoms. Fere points out that in chromatic iris asymmetry the iris
(coloured part of the eye) is most coloured on the side most affected by
arrest of development. Localisation of nervous trouble occurs on the side
most affected by hare-lip. Heuse has observed the co-existence on the same
side of congenital cataract and of deformities of the skull and chest.
Hernia is often an expression of hereditary defect (Le Double) taking the
unilateral line of least resistance. Testicle inflammations of microbic
origin (venereal or otherwise) occur as a rule on the side where hernia is
located in the groin. In one-sided malformations of ovary or testicle
(decreased or increased in size, or changed in shape or location) microbe
inflammation almost always occurs at the seat of the anomaly. This
principle is illustrated in the experiments of Dupuy.[91] Here, while as a
rule, the scions of guinea-pigs (rendered epileptic by section of the
sciatic nerve) were epileptics and had deficient toes, still in some
epilepsy resulted without the toe anomaly, while still more rarely the toe
anomaly was present without the epilepsy.
The same principle is shown by certain observations of Charin and
Gley,[92] who for five years conducted experiments calculated to throw
light on the influence on the offspring of parental reception of virus.
Either both male and female have been inoculated with the bacillus of blue
pus or its toxins, or but one animal has been inoculated. The results have
not been uniform. Most frequently there ensues sterility, abortion, or
birth of progeny that die immediately. In rare instances the offspring
survive; more rarely still are they healthy. Certain rabbits (born of
these undeveloped animals) were provided with enormous epiphyses (ends of
bones), the shafts of the bones being shortened. Two rabbits were born of
a couple of which the male alone received inoculations of sterilised
culture. Five rabbits were born of these two, of which two were normal,
and a third (whose ears were rudimentary) died in a few days. In the
remaining two the ears comprised only fragments with jagged upper edges.
The tails were but two centimetres long. The external orifice of the
vagina (one rabbit was a male and the other a female) was oblique. One of
the limbs (the hind in the male and the fore in the female) was much
shorter than its fellow, the difference being four centimetres. The
shortened limb ended in a kind of stump, there being no foot or toes.
These experiments illustrate the transformation of heredity, that is the
manifestations which show the line of least resistance that the morbid
heredity has taken. As Moreau (de Tours) remarks,[93] "An incorrect
conception of the law of heredity looks for identical phenomena in each
succeeding generation. Some have refused to admit that mental faculties
were subject to heredity, because the mental characters of the descendants
were not precisely those of the progenitors. Each generation must copy the
preceding. Father and son must present the spectacle of one being, having
two births, and each time leading the same life, under the same
conditions. But it is not in the heredity of functions, or of organic or
intellectual facts that the application of the law of heredity must be
sought, but at the very fountain-head of the organism, in its inmost
constitution. A family whose head is insane or epileptic does not of
necessity consist of lunatics or epileptics, but the children may be
idiotic, paralytic, or scrofulous. What the parents transmit to the
children is not insanity, but a vicious constitution which will manifest
itself under various forms in epilepsy, hysteria, scrofula, rickets, &c.
This is what is to be understood by hereditary transmission."
The same position has been taken by Rush,[94] the pioneer American
alienist; by Maudsley,[95] by Krafft-Ebing,[96] by Meynert, by Mercier, by
Fere,[97] and others. Morel,[98] the chief accepted apostle of the
doctrine of degeneracy, remarked, nearly at the same time as Moreau, that
"heredity does not mean the very disorder of the parents transmitted to
the children with the identical mental and physical symptoms observed in
the progenitors, but means transmission of organic disposition from
parents to children. Alienists have, perhaps, more frequent occasion than
others for observing not merely this hereditary transmission, but likewise
various transformations which occur in the descendants. They are aware
that simple neuropathy (nervous tendency) of the parents may produce in
the children an organic disposition resulting in mania or melancholia,
nervous affections which in turn may produce more serious degeneracy and
terminate in the idiocy or imbecility of those who form the last link in
the chain of hereditary transmission."
What is true of the organism as a whole is true of the cells forming its
organs. It should be remembered that while cell life is altruistic or
subordinated to the life of the organ, through the law of economy of
growth, recognised by Aristotle, and through it to the life of the
organism as a whole, altruism is not complete enough to prevent entirely a
struggle for existence on the part of the cells or the individual organs.
With rise in evolution this struggle decreases, to increase with the
opposite procedure of degeneracy. From it results the phenomenon of
arrested and excessive development.
As Dareste has shown (and the fact has been corroborated by Spitzka[99]),
embryologists can imitate natural malformation 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. Partial
varnishing or irregular heating of the egg-shell, in particular, results
in anomalies comparable to microcephaly (little head) and cerebral
asymmetry. This latter fact (showing the constancy of the injurious effect
of so apparently slight an impression as the partial varnishing of a
structure not connected with the embryo at all directly) suggests the line
of research to be followed in determining the source of the maternal and
other impressions acting on the germ. What delicate problems are to be
solved in this connection may be inferred from the fact that eggs
subjected to the vibration and shocks of a railroad journey are checked in
development for several days, or permanently arrested. A more delicate
molecular shock during the maturation of the ovum, during its
fertilisation, or finally during embryonic stages of the more complex, and
therefore more readily disturbed and distorted human germ, accounts for
the disastrous effect of insanity, emotion, or other mental or physical
shock of the parent on the offspring. The cause of the majority of
cerebral deformities exists 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 by the fact that the somatic
malformations of the hereditary forms of insanity often involve the body
elsewhere than in the nervous axis. The stigmata of heredity--defective
development of the uro-genital system, deformities of the face and skull,
irregular development of the teeth, misshapen ears and limbs--owe their
grave significance to this fact. Like deformities of the brain, these
anomalies are also more marked and constant with the lower forms of the
hereditarily based systematised perversions of the mind than the higher.
It is easy from these results to understand how far and how the nervous
system has its part in the disorders of general development. It can be
easily understood how the individuals who present most deformities are
equally those who suffer from most decided disorders of the nervous
system.
These morbid manifestations of heredity occur in certain categories,
either local as to organs or structures, or affecting the body as a whole.
These categories Moreau (de Tours) lucidly sums up as: First, absence of
conception; second, retardation of conception; third, imperfect
conception; fourth, incomplete products (monstrosities); fifth, products
whose mental, moral, and physical constitution is imperfect; sixth,
products specially exposed to nervous disorders in order of frequency as
follows--epilepsy, imbecility or idiocy, deaf-mutism, insanity, cerebral
paralysis, and other cerebral disorders; seventh, lymphatic products;
eighth, products which die in infancy in a greater proportion than sound
infants under like conditions; ninth, products which, although they escape
the stress of infancy, are less adapted than others to resist disease and
death.
The explanation of these morbid manifestations lies in the very
foundations of embryology. Bearing in mind the principles of individuation
pointed out by Spencer, it is easily understood how reversal of this
principle would produce greater and greater destruction of the complex
functions, resultant on increased reproductive power of cells (whose
environment is not suited to such reproductions) and thus lead to such a
struggle for existence as to produce sterility (from interdestruction of
the ovum cells, or the cells forming the spermatozoon). This condition is
further increased by the operation of two biologic principles. The first
relates to the cells or organs forming an organism. The second, as Von
Baer has shown, deals with the relation of the organs to each other.
Vertebrate embryos of a common type, at their origin, assume successively
a number of common forms before definitely differentiating. Dareste points
out that supernumerary organs do exist in these common forms at one phase
of embryonic life. This community of embryonic types and this last fact
explain repetition of teratologic types or monstrosities in vertebrates.
This community of origin, moreover, indicates that a higher vertebrate
embryo contains in essence the organs and potentialities of lower
vertebrates, and that under the influence of heredity or accidental defect
an organ belonging to another species may develop, or an organ constant in
a species may be lacking in an individual, without the necessity of
explaining the immediate effects by distant atavism. Some anomalies found
among degenerates recall types less elevated than man, and very distant
from him, even his possible Lemurian precursor.
It is obvious from the principles already demonstrated that the secondary
effects of infectious disorders and injuries are reproduced in various
types in the offspring. The malformations of the limbs experimentally
demonstrated to be due to ancestral infection by Charin and Gley, and to
injury by Dupuy, noticeably occur in men. Moor has observed supernumerary
fingers in an imbecile girl; her grandfather and one uncle are
polydactylous and insane. F. S. Coolidge has had under observation a case
which excellently depicts these deformities in men. Kiernan[100] reports
the case of a man whose grandfather and father had been prophets of the
Lord, as shown by the fact that on one side of the body they had six toes
and six fingers, and the two sides of the body were unequal, the
six-fingered one being smaller than the other. This father and grandfather
were highly regarded in a secluded vale in Norway as religious teachers
and for their power to cure disease by charm. The father had ten children,
of whom three were born dead and six died in infancy. Kiernan's patient
was the only survivor of this family. During boyhood he experienced
various persecutions, some by unseen agencies, some on the part of the
villagers, who towards the end of his father's life also persecuted the
father. These persecutions seem to have been withdrawal by the peasants of
their belief in the father's ability to charm sickness out of cattle,
evidently due to growing popular intelligence. This was regarded by the
father as the result of persecution by the devil, who was desirous of
trying him as Job was tried. It was revealed to him that his son should
likewise suffer persecution, which would also be the work of the devil.
The son heard unseen persons, who pointed him out in school as the son of
the sham wizard. In consequence he was avoided by all his schoolmates
except the members of one family who still retained their belief in the
father's supernatural powers. Into this family the son married; then,
pressed by his unseen persecutors, he came to the United States. Here he
worked at his trade as a carpenter, and had no return of any persecutory
delusions, although he still believed he was a prophet. On admission to
the insane hospital, twenty years after his arrival in the United States,
he was found to have such a decidedly asymmetrical body that suspicions of
general hemiatrophy were excited, but the condition was found to be
congenital. The hand and foot of the seemingly atrophic side had six
fingers and toes. The man had been sent to the insane hospital in
consequence of an altercation with a neighbour who was clearly in the
wrong; but both being arrested, the patient's _amour propre_ was aroused
and he declared his prophetship, which led to his trial and commitment as
a lunatic. His wife, who applied for his discharge, was also a paranoiac.
They had had ten children, of whom three were still living at the ages of
six, eight, and ten. Two of these were six-toed and six-fingered
unilaterally, and one of them, a boy, had the peculiar general asymmetry
of the father. The third child was seemingly normal.
The experimental results of Charin and Gley, on the degeneration produced
in offspring by ancestral microbic infection, tend to show that not merely
are the extremities affected, but in certain cases the whole organism,
along lines laid down by Moreau's categories. This is demonstrated by
study of the degeneracy stigmata of phthisical families. Alex. James,
Ricochon,[101] C. E. Paddock,[102] and others have shown that (in addition
to the ordinary stigmata) the biologic stigmata of degeneracy (such as
plural and quickly repeated births) are frequent among phthisical
families. The same phenomena often occur in families whose scions are
attacked with diabetes, obesity, articular rheumatism, cancer and gout. De
Giovanni[103] finds that particular nervous states exist in those
predisposed to tuberculosis, whom he divides into erethists (restless),
torpids, and energetics. There is a diminutive heart, whose right
ventricle has comparatively exaggerated dimensions, while the arteries
have lessened calibre.
A family illustrating excellently the transmutation of morbid heredity is
one followed through five generations by Kiernan.[104] A farmer lived
twenty miles distant from his nearest neighbour, whose only child he
married. The daughter had led a lonely life till her courtship at the age
of 28 by the farmer, then three years younger. The farmer married her for
$300, after having impregnated her. He then found lead on his farm and
went to a city. A stock-company bought his farm and launched him into the
stock market, where he made money more as a cunning tool than an
adventurer. He became a high liver, gouty and dyspeptic, and died with
symptoms of gouty kidney at 70. The couple had five children. The eldest,
a son, became a "Napoleon of Finance," but, inheriting his father's
cunning, died wealthy and within the pale of the law. He married a society
woman, the last scion of an old family. The second child, a daughter, was
club-footed and early suffered from gouty tophi. She married a society man
of old family who had cleft palate. The third child, a daughter, had
congenital squint. She married a man who suffered from migraine of a
periodical type. The fourth child, a daughter, was normal. She married a
thirty-year-old active business man, in whom ataxia developed a year after
marriage. The fifth child, a son, was ataxic at eighteen. The children of
the "Napoleon of Finance" and the society woman were an imbecile son, a
nymphomaniac, a hysteric, a female epileptic who had a double uterus, and
a son who wrote verses and was a society man. The cleft-palated society
man and club-footed woman had triplets born dead and a squinting,
migrainous son who, left penniless by his parents, married his cousin the
nymphomaniac daughter of the "Napoleon of Finance," after being detected
in an intrigue with her. The migrainous man and squinting daughter of the
farmer stockbroker had a sexually inverted masculine daughter, a daughter
subject to periodical bleeding at the nose irrespective of menstruation,
as well as chorea during childhood, a normal daughter, a deaf-mute
phthisical son, a daughter with cloacal formation of the perineum, an
ameliac son, a cyclopian daughter (with one central eye) born dead, and,
finally, a normal son. The sexual invert married the versifier son of the
"Napoleon of Finance." The progeny of the normal daughter of the farmer
stockbroker and the ataxic husband were a dead-born, sarcomatous son, a
gouty son, twin boys paralysed in infancy, twin girls normal, a normal
son, and a son ataxic at fourteen. The progeny of the nymphomaniac
daughter and her strabismic, migrainous cousin were a ne'er-do-well, a
periodical lunatic, a dipsomaniac daughter who died of cancer of the
stomach, deformed triplets who died at birth, an epileptic imbecile son, a
hermaphrodite, a prostitute, a double monster born dead, a normal
daughter, and a paranoiac son. The ne'er-do-well married his nose-bleeding
cousin. The gouty son of the farmer's normal daughter married the hysteric
daughter of the "Napoleon of Finance." They had a son born with such
general asymmetry as to seem hemiatrophic, a prostitute, dead triplets, a
male sexual invert, a colour-blind daughter, and a normal son. The
colour-blind daughter married the paranoiac grandson of the "Napoleon of
Finance." The progeny of the sexual invert and the versifier, who were
soon divorced, were a daughter with periodical nymphomania, who had some
artistic and literary ability, and a son who died of gastric cancer. The
scions of the ne'er-do-well and his nose-bleeding cousin were a moral
imbecile, a "bleeder," a stammering daughter who had an uvular deformity,
a deaf-mute with undescended testicle, dead-born triplets, an infantile
paralytic son, and dead-born quadruplets. The progeny of the paranoiac and
his colour-blind cousin were an exophthalmic daughter, an epileptic with
undescended testicle, a cleft-palated imbecile with a cloaca, dead-born
quadruplets, an idiot boy, and a "bleeder."
Doutrebente reports the following family history: First generation: Father
intelligent, became melancholic, and died insane. Mother nervous and
emotional. Second generation: Ten children; three died in childhood, seven
reach maturity as follows: Daughter A, melancholiac; daughter B, insane at
twenty; daughter C, imbecile; daughter D, a suicide; son E, imbecile; son
F, melancholic; son G, a melancholic. Third generation: A has ten
children; five die in childhood, one is deformed, one has fits of
insanity, one is eccentric and extravagant, two are intelligent and marry,
but are childless. B leaves no issue. C has one child, a deformed
imbecile. D has three children; one is an imbecile, one dies of apoplexy
at twenty-three, and the third is an artist described as "extravagant." E
has two children; one dies insane, the other disappears and is supposed to
have committed suicide. F is childless. G has one child, who is
imbecile.[105]
Strahan[106] gives a genealogy which shows very clearly the close kinship
existing between the cancerous diathesis and other forms of constitutional
degeneration whose outward manifestations are infantile convulsions,
suicide, epilepsy, insanity, lymphatism, and sterility. The father of this
family died of stomach cancer at sixty. He had a brother who cut his
throat at fifty-six; the mother, an apparently healthy woman, died of a
fit, at the age of fifty-four. To this pair seven children were born: 1. A
son who died of stomach cancer at fifty-eight. 2. A son who died in
convulsions at thirteen weeks. 3, 4, and 5. Three daughters who died of
phthisis, one at sixteen, the other two later in life, and after being
married for many years; none left any issue. 6. A son who is epileptic,
and has twice been confined in lunatic asylums; married, but no issue. 7.
A son who is sane, and enjoying fair health. Here the taint in the mother
appears to have been slight; still, it was there, and while certainly
preventing reversion, it doubtless deepened the degeneration of the
father in the children. In the father's stock the taint was much deeper.
While it was exhibited as cancer in him, it took the form of suicidal
impulse in his brother. In the children of this pair the disease of the
father is transmitted to the eldest son; but can it be denied, Strahan
asks, that the infantile convulsions, the liability to tubercular disease,
the epilepsy, the insanity, and the marked sterility were but the varying
evidences of the degenerate nature, inherited from a father who might have
died earlier of some acute disease, taking the secret of his nature with
him?
The value of the principle of atavism in off-setting degeneracy is nowhere
better illustrated than in the history of famous families of degenerates
like those of the Binswangers, of "Margaret," of the Jukes, as well as
those reported in France, Germany, Austria, Russia, and the Scandinavian
countries. The Rougon-Macquart family of Zola (which had its actual
prototype in the Kerangal family described by Aubry[107]) had, like these,
several scions in whom former normality regained its power through
atavism. Sometimes this atavism is not shown to any greater extent than a
slight modification of the abnormality or morbidity.
Telegony, the so-called and much-debated heredity of influence, whereby
the children of a second marriage resemble the first husband, may be
explained by a biologic principle demonstrable in the lower animals,
whereby conjugation not sufficient to fecundate ova is sufficient so to
impress them that when finally fecundated they bear characteristics of
the first conjugation. Its part in either normal or degenerate heredity
is but slight. Some instances charged to it might be attributed to mental
impression on the mother.
Luys[108] excellently sums up the whole question of heredity when he
remarks: "Heredity governs all the phenomena of degeneracy with the same
results and the same energy as it controls moral and physical resemblances
in the offspring. The individual who comes into the world is not an
isolated being separated from his kindred. He is one link in a long chain
which is unrolled by time, and of which the first links are lost in the
past. He is bound to those who follow him, and to the atavic influences
which he possesses; he serves for their temporary resting-place, and he
transmits them to his descendants. If he come from a race well endowed and
well formed, he possesses the characters of organisation which his
ancestors have given him. He is ready for the combat of life, and to
pursue his way by his own virtues and energies. But inversely, if he
spring from a stock which is already marked with an hereditary blemish,
and in which the development of the nervous system is incomplete, he comes
into existence with a badly balanced organisation; and his natural
defects, existing as germs, and in a measure latent, are ready to be
developed when some accidental cause arises to start them into activity."