6 BULLETIN 32, 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.—Eztent of pasteurization of milk in cities m the United States of 
more than 10,000 population in 1915 and 1921. 
wee of oe Der caw | 10t0 50 per seer Qto10 per a None 
Population of | answering. pasteurized. | SS es ES gE pasteurized. 
cities. | 
| 
| 1915 | 1921 | 1915 1921 | 1915 1921 1915 | 1921 1915 1921 
pao" -9iode flan TiOur Of “SV Sneha eats amen 
| | 
| Per ct.| Perct.| Perct. | Perct.| Perct.| Perct. | Perct. | Per ct. 
More than 500,000. - -! 9 12 77.8 | 100.0 22.2 0 0 0 0 0 
100,001 to 500,000... - .| 40 42 30.0 90.5 50.0 9.5 15.0 0 5.0 0 
75,001 to 100,000. .-... 19 15 26.3 78233 42.1 26.7 21.0 0 10.6 0 
50,001 to 75,000-...-- 30 344! 24253 67.7 50.0 14.7 20.0 2.9 16.7 14.7 
25,001 to 50,000-.-... 7 62] 16.7 59.7 39.7 25.8 15.4 2.3 28.2 11.3 
6.0 33.3 23.8 18.3 10.7 9.5 59.5 38.9 
10,001 to 25,000... ... 168 126 
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. Im 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 
hy 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. 
ee a Se ae Se ee ee a, en 
