Disease and Its Causes by William Thomas Councilman (early reader books .TXT) 📕

in tracing the ancestry of tuberculous patients it is rare to find the disease not represented in the ancestors. A further difficulty is that the environment is also inherited. The child of a tuberculous parent has much better opportunity to acquire the infection than a child without such an environment [page 167]. Other diseases than the infectious seem to be inherited, of which gout is an example. In gout there is an unusual action of the cells of the body which leads to the formation and the retention in the body of substances which are injurious. Here it is not the disease which is inherited, but the variation in structure to which the unusual and injurious action of the cells is due.

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.

In certain cases the inheritance is transmitted by the female alone. This is the case in the hæmophilia, the unfortunate subjects of which are known as bleeders. There is in this a marked tendency to hæmorrhage which depends upon an alteration in the character of the blood which prevents clotting. This, the natural means of stopping bleeding from small wounds, being in abeyance, fatal hæmorrhage may result from pulling a tooth or from an insignificant wound. There is a seeming injustice in the inheritance, for the females do not suffer from the disease although they transmit it, while the males who have the disease cannot even create additional sympathy by transmitting it.

The most obvious inheritance is seen in the case of malformations. These represent wide departures from the type of the species as represented in the form. There is no hard and fast line separating the slight departures from the normal type known as variations and mutations, from the malformations. Certain of the malformations known as monstrosities hardly represent the human type. These are the cases in which the foetus is represented in a formless mass of tissue, or there is absence of development of important parts such as the nervous system or there is more or less extensive duplication of the body. There has always been a great deal of popular interest attached to the malformations owing to the part which maternal impressions are supposed to play in their production. In this, some striking impression made on the pregnant woman is supposed to affect in a definite way the structure of the child. The cases, for instance, in which a woman sees an accident involving a wound or a loss of an arm and the child at birth shows a malformation involving the same part. There is no association between maternal impressions and malformations, although there have been many striking coincidences. All malformations arise during the first six weeks of pregnancy known as the embryonic period, in which the development of the form of the child is taking place, and during which time there is little consciousness of pregnancy. Maternal impressions are usually received at a later period, when the form of the child is complete and it is merely growing. It must be remembered also that there is neither nervous nor vascular connection between the child in the uterus and the mother, the child being from the period of conception an independent entity to which the mother gives nutriment merely. Of course, as has been said, the mother may transmit to the child substances which are injurious, and in certain cases parasites may pass from the mother to the foetus. The same types of malformations which occur in man are also seen in birds, and it would require a more vigorous imagination than is usual to believe that a brooding hen could transmit an impression to an egg and that a headless chick could result from witnessing the sacrifice of an associate. The idea of the importance of maternal impressions in influencing the character of the offspring is a very old one, a well-known instance being the sharp practice of Jacob's using peeled wands to influence the color of his cattle. In regard to coincidences the great number of cases in which strong impressions made on the mind of the pregnant mother without result on the offspring are forgotten. The belief has been productive of great anxiety and even unhappiness during a period which is necessarily a trying one, and should be dismissed as being both theoretically impossible and unsupported by fact.

The malformations are divided anatomically into those characterized, first, by excess formation, second, by deficient formation, third, by abnormal displacement of parts. They are due to intrinsic causes which are in the germ, and which may be due to some unusual conditions in either the male or female germ cell or an imperfect commingling of the germinal material, and to extrinsic causes which physically, as in the nature of a shock or chemically as by the action of a poison, may affect the embryo through the mother. Malformations are made more numerous in chickens by shaking the eggs before brooding. A number of malformations are produced by accidental conditions arising in the environment; for instance, the vascular cord connecting mother and child may become wound