CHAPTER VII
Contagious and Infectious Disease
Among the gains of human advance in evolution stand out prominently complete immunity from certain diseases due to germs, and partial immunity from others, which last immunity results in chronic types, rather than in acute, because of increased vital resistance in man. Tuberculosis and dourine, acute diseases in the cow and horse, have become chronic diseases, tuberculosis (or consumption) and syphilis, in man. Such chronicity is evidence of advance, yet it constitutes an element of degeneracy, since the victim of the chronic disease is able to leave more offspring than would be possible were the disorder acute. In other respects acute and chronic contagions and infections exert the same influence in regard to degeneracy. The germ of the disease may be inherited, or general nutrition of the fœtus may be so checked in development that the child inherits a predisposition to disease.
Through this check to fœtal development the phagocytes, or white blood cells, become so weakened that they are unable to devour fœtal structures as useless to man as the tadpole’s tail (which it devours) is useless to the developed frog. This power being weakened, the organs which form antitoxins (or protective tonics against disease), from lack of development fail to perform their function. For this reason in the degenerate many infections and contagions assume their old destructive type.
The influence of these disorders in the parent may result in the bony mal-development shown to occur in animals by Charrin and Gley, and in man by Coolidge. The facial bones, jaw, and teeth are peculiarly liable to be thus affected. Though the effect of the disease on the parent be but temporary, the child’s development may be checked as to higher tendencies. Thus mothers have borne moral imbeciles, epileptics or lunatics, after a pregnancy during which they were attacked by contagious disease, albeit the children of subsequent and previous pregnancies were normal.
The children of pregnancies previous to the one complicated by the contagious disease may be healthy, while those of subsequent pregnancies are defective. Any contagious or infectious disease may not only interfere temporarily with the bodily strength, but may produce complete change in the parent’s system extending even to the highest acquirement of man. In some occur changes thus graphically described by Bulwer: “There have been men who, after an illness in which life itself seemed suspended, have arisen as out of a sleep with characters wholly changed. Before gentle, good, and truthful, they now become bitter, malignant, and false. To those whom they before loved they evince repugnance and loathing. Sometimes this change is so marked and irrational that their kindred ascribe it to madness. Not the madness which affects them in the ordinary business of life, but that which turns into harshness and discord the moral harmony which results from natures whole and complete.”
The nerve centres controlling nutrition, growth, repair, secretion, and excretion are often as deeply affected as those checks constituting morality. At the periods of physiologic stress these effects are especially noticeable. Moral insanity, intellectual insanity, unequal mental balance, hysteria, precocious sexuality, unconscious mendacity, mental parasitism (the germ of pauperism), epilepsy, neuroses, and all types of nutritive and constitutional defects result. The nutritional defects may appear chiefly in the walls of the blood vessels and lymphatics. While these are most common in the chronic infections and contagions, they often occur in acute typhoid fever, scarlatina, diphtheria, whooping-cough, &c. Proper blood supply and utilisation of waste is thus prevented. Organs cannot perform their function, and are predisposed to disease from disuse and from weakness of the disease-fighting phagocytes and antitoxins. From this results irregularity of organ function, which is hereditarily transmissible. The weakened vessel walls yield to strain, and thus produce local stomach, bowel, liver, gland, and kidney disorders. This organ weakness may alone be transmitted to the offspring. The functions of the great glands (thyroid, thymus, suprarenals, pituitary body, bone-marrow, testicles and ovaries) which secrete principles necessary to the equal balance of nutrition are perverted. The liver, in the acute but more particularly the chronic contagions, paralysed in nerve tone, fails in its function of poison-destroyer, as for the same reason the kidneys fail in their power of ejecting hurtful waste. Through this interaction of perverted nutrition, imperfect poison-destruction, and deficient waste ejection result and continue the states of nervous exhaustion after the contagions and infections. Thus nerve exhaustion with its suspicion, its capricious hopefulness and gaiety, is practically continuous in tuberculosis, syphilis, and leprosy.
The acute and chronic contagions and infections so lower cell vitality through the perverted functions described that inert connective tissue replaces healthy working cells. This is especially the case with syphilis, which, when driven from the system, leaves behind it a tendency to disease based on this connective tissue increase. This tendency, latent in the ancestor, may be so intensified in the descendant as to produce the hereditary ataxias (loss of movement power), and like neuroses. At the periods of stress such tendencies are peculiarly potent, and not only check, but reverse development. The chronic contagions and infections are most fertile sources of human degeneracy since their weakened products are enabled to survive under modern beneficence. Of these chronic contagions two (tuberculosis and syphilis) alone deserve attention, since the third (leprosy) exerts but little influence. Despite its existence for more than a century (New Brunswick and Nova Scotia on the north and Louisiana on the south) on the borders of the United States, despite its subsequent importation from Norway, Sweden, China, and Hawaii, its spread has been infinitesimal, and its influence on race deterioration is still less demonstrable.