transmitted by sexual contact such as syphilis and gonorrhoea.  It is of importance that the facts bearing on the hereditary transmission of disease should become of general knowledge, in order that the dangers may be known and voluntarily avoided.  No measures of preventive medicine are successful which are not supported by a public educated to appreciate their importance, and the same holds true of eugenics.  How successful will be public measures leading to the prevention of offspring in the obviously unfit by sterilization of both males and females is uncertain.  It is doubtful whether public sentiment at the present time will allow the measure to be thoroughly carried out.  Some results in preventing unfit heredity may be attained by the greater extension of asylum life, but the additional burden of this upon the labor of the people would be difficult to bear.  At best such measures would only be carried out in the lower class of society.

CHAPTER XI

CHRONIC DISEASES.—­DISEASE OF THE HEART AS AN EXAMPLE.—­THE STRUCTURE AND FUNCTION OF THE HEART.—­THE ACTION OF THE VALVES.—­THE PRODUCTION OF HEART DISEASE BY INFECTION.—­THE CONDITIONS PRODUCED IN THE VALVES.—­THE MANNER IN WHICH DISEASE OF THE VALVES INTERFERES WITH THEIR FUNCTION.—­THE COMPENSATION OF INJURY BY INCREASED ACTION OF HEART.—­THE ENLARGEMENT OF THE HEART.—­THE RESULT OF IMPERFECT WORK OF THE HEART.—­VENOUS CONGESTION.—­DROPSY.—­CHRONIC DISEASE OF THE NERVOUS SYSTEM.—­INSANITY.—­RELATION BETWEEN INSANITY AND CRIMINALITY.—­ALCOHOLISM AND SYPHILIS FREQUENT CAUSES OF INSANITY.—­THE DIRECT AND INDIRECT CAUSES OF NERVOUS DISEASES.—­THE RELATION BETWEEN SOCIAL LIFE AND NERVOUS DISEASES.—­FUNCTIONAL AND ORGANIC DISEASE.—­NEURASTHENIA.

Chronic diseases are diseases of long duration and which do not tend to result in complete recovery; in certain cases a cause of disease persists in the body producing constant damage, or in the course of disease some organ or organs of the body are damaged beyond the capacity of repair, and the imperfect action of such damaged organs interferes with the harmonious inter-relation of organs and the general well-being of the body.  The effect of damage in producing chronic disease may not appear at once, for the great power of adaptation of organs and the exercise of reserve force may for a time render the damage imperceptible; when, however, age or the supervention of further injury diminishes the power of adaptation the condition of disease becomes evident.  Chronic disease may be caused by parasites when the relation between host and parasite is not in high degree inimical, as in tuberculosis, gonorrhoea, syphilis, most of the trypanosome diseases and the diseases produced by the higher parasites.  In certain cases the chronic disease represents really a series of acute onsets; thus in the case of the parasites there may be periods of complete quiescence of infection but not recovery, the parasites remaining