BULLETIN 342, U. 
S. DEPARTMENT OP AGRICULTURE 
carried on more or less secretly, and, 
except as a means of preserving the 
milk, was regarded by them as a proc- 
ess of no value. As the practice be- 
came more general the subject of Pas- 
teurization was studied, and its value 
as a means; of destroying disease- 
producing bacteria was recognized. In 
consequence of the recognition of the 
merits of the process there has been 
during the last 20 years a rapid in- 
crease in the quantity of milk Pasteur- 
ized. Jordan (23), in a paper pub- 
lished in 1913, stated that 10 years 
previously only about 5 per cent of 
the milk supply of New York City 
was Pasteurized ; figures from other 
sources show that about 40 per cent 
in 1912, 88 per cent in 1914, and 98 
per cent in 1921 was Pasteurized. In 
Boston very little milk was Pasteur- 
ized in 1902, but in 1915 80 per cent, 
and in 1924 about 97 per cent, was 
so treated. In many of the smaller 
cities there have been corresponding 
increases in the quantity of milk Pas- 
teurized during the last few years. 
The general tendency in this coun- 
try to-day is toward the Pasteuriza- 
tion of all milk for direct consump- 
tion, with the exception of certified 
or equivalent grades of milk from 
tuberculin-tested herds. Some idea of 
the increase in the extent of Pasteur- 
ization in the United States from 1915 
to 1924 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 on 328 in 1924. 
Table 1. 
-Extent of Pasteurization of milk in cities in the United States in 
1915 and 1924 
Population of cities 
Number of 
cities 
90 to 
100% 
milk 
Pas- 
teur- 
ized 
50 to 
90% 
milk 
Pas- 
teur- 
ized 
50 to 100% 
milk 
Pasteurized 
10 to 50% 
milk 
Pasteurized 
to 10% 
milk 
Pasteurized 
None 
Pasteurized, 
per cent 
1915 
1924 
1924 
1924 
1915 
"1924 
1915 
1924 
1915 
1924 
1915 
1924 
More than 500,000 
9 
40 
19 
30 
78 
168 
9 
37 
19 
25 
00 
105 
73 
% 
100.0 
56.8 
26.3 
20.0 
20.0 
12.4 
5.5 
% 

35.1 
47.3 
60.0 
60.0 
°>° 3 
35^6 
% 
77.8 
30.0 
26.3 
12.3 
16.7 
6.0 
% 
100.0 
91.9 
73.6 
80.0 
80.0 
45.7 
41.1 
% 
22.2 
50.0 
42.1 
50.0 
39.7 
23.8 
% 

8.1 
15.8 
12.0 
13.3 
31.4 
27.4 
% 

15.0 
21.0 
20.0 
15.4 
10.7 
% 


10.6 
8.0 
5.0 
2.9 
2.7 
% 

5.0 
10.6 
16.7 
28.2 
59.5 
% 

100,001 to 500,000 . 

75 001 to 100,000 . 

50 001 to 75,000. 

25,001 to 50,000.-- - .- 
1.7 
10,001 to 25,000 
20.0 
28.8 

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 Pas- 
teurized. There has been during the 
same period a marked decrease in the 
percentage of cities having no Pas- 
teurized milk. It seems evident that 
the process of Pasteurization 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 in- 
terest. In 1915 milk was Pasteurized 
in about 62 per cent of the cities with 
a population above 10,000, and in 1924 
in about 89 per cent of such cities. 
The increase in Pasteurization in small 
cities with a population of 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 80 per cent in 1924. 
Considering these figures as a whole 
the increasing trend of Pasteurization 
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 increasing tendency, which fol- 
lows their increasing population, for 
cities to have Pasteurized milk and 
also to Pasteurize a higher percentage 
oi: the supply. 
Table 2. — Proportion of cities having 
Pasteurized- milk and average per 
cent of their milk supply which teas 
Pasteurized in 1924 
Population of cities 
Num- 
ber of 
cities 
re- 
port- 
ing 
Pas- 
teur- 
ized 
milk 
Num- 
ber of 
cities 
with 
no 
Pas- 
teur- 
ized 
milk 
Per 
cent 
of 
cities 
hav- 
ing 
Pas- 
teur- 
ized 
milk 
Aver- 
age 
per 
cent 
of 
milt 
Pas- 
teur- 
ized 
More than 500,000.-- 
100,001 to 500.000 
75,001 to 100.000 
50,001 to 75.000 
25,001 to 50.000. 
10,001 to 25,000 
Less than 10,000 
9 
37 
19 
25 
58 
84 
53 




2 
21 
20 
100. 00 
100. 00 
100. 00 
100. 00 
94.4 
80.0 
72.6 
98.1 
81.7 
66.6 
66.6 
67.0 
42.5 
33.6 
Total 
285 
43 
