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