PREVENTIVE MEDICINE. 355 



increase in population, notwithstanding the general improvement in 

 the sanitary condition of towns and cities. This is no doubt due to the 

 continued pollution of water supplies and to the extension of this 

 infectious disease in rural districts. It is in fact now an endemic dis- 

 ease in nearly all parts of the United States. 



According to the census report of 1900, there were 111,000 deaths 

 from tuberculosis during the year 1900. This does not, however, in- 

 clude the deaths in certain states in which the vital statistics are incom- 

 plete or unreliable, and it is probable that there are at least 145,000 

 victims of the great white plague annually within the limits of the 

 United States. The last census return in those states where registration 

 was approximately correct, including a population of about 21,000,000 

 people, shows that 12 per cent, of all deaths resulted from pulmonary 

 tuberculosis, 8.5 per cent, from pneumonia, 3 per cent, from typhoid 

 fever and 3 per cent, from diphtheria and croup. These figures indi- 

 cate to some extent the task which preventive medicine has still to 

 accomplish. 



A most interesting and notable example of the beneficent results 

 following the practical application of sanitary measures based upon 

 exact knowledge relating to the etiology of an infectious disease 

 is afforded by the recent extinction of yellow fever in the city of 

 Havana, which for many years had been the principal focus of infection 

 in the West Indies, and the port from which it has been repeatedly 

 carried to the seaport cities of the United States. According to the 

 reports of the health officers in that city, there has not been a case of 

 yellow fever in Havana for more than a year, and the extinction of the 

 disease is ascribed entirely to the vigorous measures enforced to prevent 

 its transmission by mosquitoes of the species proved by the researches of 

 Reed and Carroll to be the immediate hosts of the yellow fever parasite 

 and the active agents in the transmission of the disease from man to 

 man. During the first sixty years of the past century, yellow fever pre- 

 vailed almost annually in one or more of the southern seaports of the 

 United States and not infrequently it extended its ravages to the in- 

 terior towns in one or more of the southern states. So frequently did 

 it prevail during the summer months in New Orleans and Charleston 

 that the permanent residents of those cities commonly regarded it as a 

 disease of the climate and a necessary evil which it was folly to attempt 

 to combat by quarantine restrictions. 



In the great epidemic of 1853, yellow fever prevailed extensively in 

 the states of Florida, Alabama, Louisiana, Mississippi, Arkansas and 

 Texas. The epidemic of 1867 was limited to the states of Louisiana 

 and Texas. Those states again suffered severely in 1873 and the states 

 of Florida, Alabama and Mississippi were also invaded. A still more 

 extended and deadly epidemic occurred in 1878, causing a mortality 



