SECONDARY TERMINAL AND MIXED INFECTIONS.--THE EXTENSION OF INFECTION IN THE INDIVIDUAL.--TUBERCULOSIS.--THE TUBERCLE BACILLUS.--FREQUENCY OF THE DISEASE.--THE PRIMARY FOCI.--THE EXTENSION OF BACILLI.--THE DISCHARGE OF BACILLI FROM THE BODY.--INFLUENCE OF THE SEAT OF DISEASE ON THE DISCHARGE OF BACILLI.--THE INTESTINAL DISEASES.--MODES OF INFECTION.--INFECTION BY SPUTUM SPRAY.--INFECTION OF WATER SUPPLIES.--EXTENSION OF INFECTION BY INSECTS.--TRYPANASOME DISEASES.--SLEEPING SICKNESS.--MALARIA.--THE PART PLAYED BY MOSQUITOES.--PARASITISM IN THE MOSQUITO.--INFECTION AS INFLUENCED BY HABITS AND CUSTOMS.--HOOKWORM DISEASE.--INTERRELATION BETWEEN HUMAN AND ANIMAL DISEASES.--PLAGUE.--PART PLAYED RATS IN TRANSMISSION.--THE PRESENT EPIDEMIC OF PLAGUE 159 CHAPTER IX DISEASE CARRIERS.--THE RELATION BETWEEN SPORADIC CASES OF INFECTIOUS DISEASE AND EPIDEMICS.--SMALLPOX.--CEREBROSPINAL MENINGITIS.--POLYOMYELITIS.--VARIATION IN THE SUSCEPTIBILITY OF INDIVIDUALS.--CONDITIONS WHICH MAY INFLUENCE SUSCEPTIBILITY.--RACIAL SUSCEPTIBILITY.--INFLUENCE OF AGE AND SEX.--OCCUPATION AND ENVIRONMENT.--THE AGE PERIOD OF INFECTIOUS DISEASES 185 CHAPTER X INHERITANCE AS A FACTOR IN DISEASE.--THE PROCESS OF CELL MULTIPLICATION.--THE SEXUAL CELLS DIFFER FROM THE OTHER CELLS OF THE BODY.--INFECTION OF THE OVUM.--INTRAUTERINE INFECTION.--THE PLACENTA AS A BARRIER TO INFECTION.--VARIATIONS AND MUTATIONS.--THE INHERITANCE OF SUSCEPTIBILITY TO DISEASE.--THE INFLUENCE OF ALCOHOLISM IN THE PARENTS ON THE DESCENDANTS.--THE HEREDITY OF NERVOUS DISEASES.--TRANSMISSION OF DISEASE BY THE FEMALE ONLY.--HEMOPHILIA.--THE INHERITANCE OF MALFORMATIONS.--THE CAUSES OF MALFORMATIONS.--MATERNAL IMPRESSIONS HAVE NO INFLUENCE.--EUGENICS 197 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 219 CHAPTER XII