I 3 2 INFECTION AND IMMUNITY 



10,000), after which a gradual reduction occurred until 

 the census year 1900, when the very low rate of 

 1.98 was reached. In New York the typhoid rate 

 was 4.47 per 10,000 inhabitants in 1870, and it has 

 only slightly exceeded this figure in two years since 

 that date (4.77 in 1881 and 4.72 in 1883). Since 

 1893 it has been constantly below 2 per 10,000 inhabit- 

 ants, a rate which probably to a large extent repre- 

 sents cases in which infection occurred outside of the 

 city at summer resorts, etc. 



In Philadelphia the typhoid death-rate has been 

 constantly above that of New York, as might be ex- 

 pected from the superior advantages enjoyed by the 

 last-named city in its water supply from the Croton 

 River. The highest typhoid death-rate recorded for 

 the city of Philadelphia during the past thirty years 

 was 9.22 per 10,000 in the year 1876, the lowest 3.24 

 in the year 1894. The average has been about 5.6, 

 which is but little below the death-rate for the city of 

 Washington in the year 1900 as given in the above 

 table. 



In Boston the typhoid mortality has fluctuated 

 between 8.62 per 10,000 in 1872 and 2.55 in 1900, the 

 latter rate being the lowest recorded during a period 

 of thirty years. 



Without doubt a majority of typhoid-fever epi- 

 demics are due to infection of the water supply by 



