49 
cent of the 670 cases, or 9 per cent of the 523 cases, attributable to 
milk infection. 
Attention is called to the difference for the two years in the ratios 
of number of typhoid cases to amount of milk sold of the two large 
milk dealers who had outbreaks of typhoid fever among their custom- 
ers in 1906 but not in 1907 (see Chart Xo. 3 of Hygienic Laboratory 
Bulletin 35 and Chart Xo. 4 of this bulletin), thus: 
yiimher of cases per 100,000 gallons of milJc sohL 
1906. ' 1907. 
Milk dealer No. 4 • 
i 
52.5 1 21.6 
Milk dealer No. 13 _ . _ 
113.9 ' 6.5 
1 1 
Of the 866 cases iiiA^estigated by us in 1906, about 10 
per cent were 
attributed to infection conveyed by milk in the course of pronounced 
outbreaks among the customers of three milk dealers. 
Besides these cases, quite definitely attributable to infected milk, 
there no doubt were, during both years, scattering cases due to, but 
which could not be traced to, milk. The number of such cases is of 
course problematical. 
The large proportion of cases of typhoid fever in families of the 
better class and the conspicuously large proportion of cases among 
children in AYashington suggest that milk pla}^s a larger part in the 
spread of the infection than we have been able to definitely determine 
by epidemiological studies. A study of Chart Xo. 3 of Hygienic 
Laboratory Bulletin 35 and the corresponding chart (Xo. 4) of this 
bulletin seems to support such a view. In this connection it is inter- 
esting to note that for both 1906 and 1907 milk dealer Xo. 10 had a 
conspicuously small number of cases of typhoid fever proportionate 
to the amount of milk sold. This dealer is the only one in lY ashing- 
ton Avho both sterilizes the bottles and pasteurizes the milk. The 
low typhoid fever rate among the customers of milk dealer Xo. 10 
is significant, and perhaps is a fair index of the result Avhich Avould 
be accomplished by the pasteurization of the general milk supply of 
Washington. 
Considering only the cases definitely attributable to milk and the 
number of secondary cases contracting the infection directly or in- 
directly from them, it is evident that the milk problem in the District 
of Columbia is grave and important, and one requiring the serious 
attention of sanitary authorities. 
The milk supply of Washington is obtained from about 1,000 dairy 
farms scattered through Virginia, Maryland, the District of Colum- 
bia, and a few eA^en in Pennsyh^ania and XeAA" York. Some of this 
milk is sent directly from the dairy farms to the consumer; the bulk 
40219—08 4 
