102 ELEMENTS OF GENERAL SCIENCE 



or to the length of time they have been allowed to stand 

 in places favorable to the growth of the bacteria (fig. 50). 

 Thus, in the city of St. Paul, Minnesota, in a special inves- 

 tigation it was found that in samples of milk secured from 

 delivery wagons there were 409,477 bacteria per cubic cen- 

 timeter, while " dipped store milk " milk which had been 

 standing in bulk contained 8,206,000 bacteria per cubic 

 centimeter. In Newark, New Jersey, it was found that 

 " bottled wagon milk " contained 416,000 bacteria per cubic 

 centimeter, while " dipped wagon milk " contained 3,623,333 

 bacteria per cubic centimeter ; that milk delivered to a store 



GERM DISEASES ALL OTHER DISEASES 



1870-79 ^..^. i^ 14.60 



1890-99 ^^^ 1^ ^^^ 11.07 ^_ 7.40 



1900-09 ^ -i^^ 7.27 _____ 7.03 



FIG. 61. A comparison of death rates 



The diagram shows the number of deaths, per 1000 population, from germ 



diseases and from all other diseases, in one of the largest American cities. As 



knowledge and care have increased, the number of deaths from preventable 



diseases has decreased 



contained at the time of its delivery 280,000 bacteria per 

 cubic centimeter, while eight hours after its delivery the num- 

 ber had increased to 1,488,000 bacteria per cubic centimeter. 

 In many cities the law now requires that milk be bottled 

 before distribution. 



117. Results of improved hygienic conditions. There are 

 many unquestioned instances of lowering the human death 

 rate through improvement of hygienic conditions (fig. 51). 

 In the city of Chicago, prior to 1908, less than 2 per cent of 

 the milk was pasteurized, and the average death rate from 

 typhoid fever per 100,000 population was 24.8. In the years 

 1909-1911 between 50 and 75 per cent of the milk was 

 pasteurized, and the average death rate per year from typhoid 

 fever per 100,000 population was 12.4; in 1916 the death 

 rate had decreased to 5.1 per 100,000. 



