BULLETIN 342, U. S. DEPARTMENT OF AGRICULTURE. 



certified or equivalent grades of milk from tuberculin-tested herds. 

 Some idea of the increase in the extent of pasteurization in the United 

 States from 1915 to 1921 may be gained by a study of Table 1. The 

 figures were obtained from a questionnaire sent to health officers. In 

 1915 the figures were based on 344 replies and 379 in 1921. 



TABLE 1. Extent of pasteurization of milk in cities m the United States of 

 more than 10,000 population in 1915 and 1921. 



It will be noted that since 1915 there has been a great increase in 

 the percentage of cities in which more than 50 per cent of the milk 

 is pasteurized. There has been during the same period a marked 

 decrease in the percentage of cities having no pasteurized milk. 



Table 1 does not contain any data from cities of less than 10,000 

 population, but replies from 88 such cities showed the following 

 figures : In 22 cities 50 per cent or more of the milk was pasteurized, 

 in 12 others from 11 to 50 per cent, and in two cities 10 per cent 

 or less was so treated. Fifty-two of the 88 cities reported no pas- 

 teurized milk. It seems evident, therefore, that the process of pas- 

 teurization is being used extensively in this country even in the 

 small cities. 



A study of the available figures on the extent of pasteurization 

 revealed a few more facts which may be of interest. In 1915 milk 

 was pasteurized in about 62 per cent of the cities with a population 

 above 10,000, and in 1921 in about 80 per cent of such cities. The 

 increase in pasteurization in small cities, 10,000 to 25,000, is shown 

 by the fact that in 1915 about 40 per cent of these cities reported 

 pasteurized milk compared with approximately 61 per cent in 1921. 



Considering these figures as a whole the increasing trend of pas- 

 teurization is plain. 



A good idea of the present extent of pasteurization may be 

 obtained from Table 2. It will be observed that there is an increas- 

 ing tendency, which follows their increasing population, for cities 

 to have pasteurized milk and also to pasteurize a higher percentage 

 of the supply. 



