21 
year it was in persons from 15 to 19. It will be noted that this year, 
as in 1907, the rate among children under 15 years of age was dispro- 
portionately high. 
By decades, 106 of the cases were under 10 years of age, 175 between 
10 and 20, 151 between 20 and 30, 74 between 30 and 40, 25 between 
40 and 50, and 11 over 50. 
The special prevalence of the disease among children observed 
during all three of the years in wdiich we have studied the situation 
suggests that milk and contact are two important factors in the 
transmission of the infection in 'Washington. (See pages 15-17, 
Keport No. 2, Hyg. Lab. Bull. No. 44.) 
LENGTH OF RESIDENCE IN THE DISTRICT OF COLUMBIA. 
The following table gives the length of residence in the District of 
Columbia of the persons affected. The cases for 1907 of correspond- 
ing duration of residence in the District of Columbia are placed in a 
parallel column. 
Length of residence. 
Number of cases. 
1908. 
1907. 
Under 6 months 
19 
20 
6 months to 1 year 
10 
15 
1 to 2 years 
22 
28 
2 to 3 years 
21 
16 
3 to 4 years 
13 
19 
4 to 5 years ....... 
13 
17 
5 to 10 years 
55 
62 
10 to 15 years 
28 
26 
15 to 20 years 
26 
16 
20 to 30 years 
19 
18 
30 to 40 years . . . 
6 
7 
40 to 50 years 
2 
4 
50 to 60 years 
1 
1 
All of life 
294 
239 
Not determined 
13 
35 
Total 
542 
523 
The ages of the persons affected in the 1908 period and who had 
resided in the District all of their lives were as follows : 
Ages. 
Cases. 
Ages. 
Cases. 
0 to 4 years 
22 
35 to 39 years 
8 
5 to 9 years 
63 
40 to 44 years 
0 
10 to 14 years 
65 
45 to 49 years 
2 
15 to 19 years 
59 
50 to 54 years 
2 
20 to 24 years 
36 
65 to 69 years 
1 
25 to 29 years 
30 to 34 years 
21 
15 
Total 
294 
