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Page 49
While tuberculosis and gout represent instances in which, although the
disease itself is not inherited yet the presence of the disease in the
ascendants so affects the germinal material that the offspring is more
susceptible to these particular diseases, much more common are the
cases in which disease in the parents produces a defective offspring,
the defect consisting in a general loss of resistance manifested in a
variety of ways, but not necessarily repeating the diseased condition
of the parent. In these cases the disease in the parents affects all
the cells of the body including the germinal cells, and the defective
qualities in the germ cells will affect the cells of the offspring
which are derived from these. There is a tendency in these cases to
the repetition in the offspring of the disease of the parents, because
the particular form of the parental disease may have been due to or
influenced by variation of structure. One of the best examples of
affection of the offspring by diseased conditions of the parents
produced by a toxic agent which directly or indirectly affects all the
cells of the body is afforded by alcohol when used in excess. Since
drunkenness has become a medical rather than a moral question, a great
deal of reliable data has accumulated in regard to it as a factor in
the heredity of disease. Grotjahn gives the following examples: Six
families were investigated in which there were thirty-one children. In
all these families the father and grandfather on the father's side
were chronic alcoholics, and in certain of the families drunkenness
prevailed in the more remote ancestors. The following was the fate of
the children: eight died shortly after birth of general weakness,
seven died of convulsions in the first month, three were malformed,
three were idiotic, three were feeble-minded, three were dwarfs, three
were epileptics, two were normal. In a second group of three families
there were twenty children. The fathers were drunkards, but their
immediate ancestors were free: four children died of general weakness,
three of convulsions in the first month, two were feeble-minded, one
was a dwarf, one was an epileptic, seven were normal. In a family in
which both father and mother and their ancestors were drunkards there
were six children: three died of convulsions within six months, one
was an idiot, one a dwarf, and one an epileptic. For comparison there
were taken from the same station in life ten families in which there
was no drunkenness: three children died from general weakness, three
from intestinal troubles, two of nervous affection, two were
feeble-minded, two were malformed, fifty were normal. Legrain has
studied on a larger scale the descendants of two hundred and fifteen
families of drunkards in which there were eight hundred and nineteen
children. One hundred and forty-five of these were insane, sixty-two
were criminals, and one hundred and ninety-seven drunkards. Of course
all this cannot be attributed to alcohol alone. There is first to be
considered a probable variation in the nervous system which is
expressed in the alcoholic habit; second, the environment consisting
in poverty, bad associates, etc., which the alcoholic habit brings;
third, the alcohol alone. That defective inheritance so frequently
takes the form of alcoholism is largely due to the environment. There
has never been the opportunity to study on a large scale the effect of
the complete deprivation of alcohol from a people living in the
environment of modern civilization. There is a possibility, and even
probability, that the defective nervous organization which predisposes
to alcoholism would seek satisfaction in the use of some other
sedative drug. So complex are all the interrelations of the social
system that it would be possible to regard alcohol as an agent useful
in removing the defective, were it not for its long-enduring action
and its effects on the descendants, procreation not being affected by
its use.
Diseases of the nervous system are particularly apt to affect the
offspring, and often the inherited condition repeats that of the
parents. This is due to the fact that most of the nervous diseases
depend both upon intrinsic factors which consist in some defective
condition of the nervous system representing a variation, and
extrinsic factors due to environment or occupation which make the
basal condition operative. The definite relation between alcoholism
and insanity is due to alcohol acting not as an intrinsic but an
extrinsic factor, bringing into effectiveness the hereditary weakness
of the nervous system. The influence of heredity in producing insanity
is variously estimated at from twenty-six per cent to sixty per cent
of all cases. This great difference in the estimation of the
hereditary influence is due to the personal equation of the
statistician, and the care with which other factors are eliminated. In
the more severe form of the hereditary degeneration the same
pathological conditions are repeated in the descendants. In certain
cases the severity of the condition increases from generation to
generation. According to Morel there may be merely what is recognized
as a nervous temperament often associated with moral depravity and
various excesses in the first generation; in the second, severe
neuroses, a tendency to apoplexy and alcoholism; in the third, psychic
disturbances, suicidal tendencies and intellectual incapacity; and in
the fourth, congenital idiocy, malformations and arrests of
development. There are some very definite data with regard to
inheritance in the nervous disease known as epilepsy. The essential
condition in this consists in attacks of unconsciousness, usually
accompanied by a discharge of nerve force shown in convulsions, the
attack being often preceded by peculiar sensations of some sort known
as the aura. In the most marked forms of the affection heredity plays
but little part, owing to the early supervention of imbecility and
helplessness, and it is a greater factor in the better classes of
society than in the proletariat. In the better classes, owing to the
greater care of the cases and the avoidance of exciting causes of the
attacks, the disease is better controlled and rarely advances to the
extent that it does among the poor. The association of epilepsy and
alcoholism is especially dangerous, for a slight amount of alcohol may
greatly accentuate the disease. In five hundred and thirty-five
children in whose parentage there were sixty-two male and seventy-four
female epileptics, twenty-two were born dead, one hundred and
ninety-five died from convulsions in infancy, twenty-seven died in
infancy from other causes, seventy-eight were epileptics, eleven were
insane, thirty-nine were paralyzed, forty-five were hysterical, six
had St. Vitus's dance, one hundred and five were ordinarily healthy.
That variations in the nervous system which produce more or less
unusual mental peculiarities and which do not take the form of nervous
disease are inherited, the most superficial consideration shows. A
child in its mental characteristics is said to take after one or the
other of its parents, certain habits and mental traits are the same,
often even the handwriting of a child resembles that of a parent.
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