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in an ambulant and unrecognized form, or of some one who has had 
the disease months or even years before (chronic bacillus carriers). 
Besides the large groups of cases of typhoid fever caused by in- 
fected milk, there must be in large cities frequently single cases or 
small groups of cases which are due to infection in the milk and yet 
can not be traced to that source. In a community where factors, other 
than milk were operating to cause a rather' extensive prevalence of 
typhoid fever, five or six cases occurring within a few days among 
the customers of a dairyman supplying several hundred families with 
milk would direct some suspicion toward that milk supply, but if 
this small group of cases should not be followed by an unusually 
large number of cases on the route of this dairyman and no typhoid 
cases were found on the dairy farm or at the dairy, these 5 or 6 cases 
would be placed by the investigator among those due to causes unde- 
termined or to causes other than milk. In many such instances, how- 
ever, these groups of cases are doubtless due to infection introduced 
in one of the many possible ways — hands, clothes, flies, water for 
washing cans, etc. — into a part of the dairyman’s output of milk for 
perhaps only one day. 
In cities having milk supplied by a number of dairymen, if several 
of these small groups of cases among customers of different dairy- 
men occur at about the same time, a list of the farms supplying each 
of the suspected dairies should be studied, and if it is found that two 
or more of these dairies receive milk from any one farm, an investiga- 
tion should be made of that farm, and in this way the source of the 
infection for the several groups of cases may be determined. 
MEASURES TO PREVENT THE DISSEMINATION OF THE INFEC- 
TION OF TYPHOID FEVER IN MILK. 
(a) The prevention of the introduction of infection into milk . — - 
This at once suggests itself as the proper measure; but the difficulty 
of carrying it out practically becomes evident when we consider the 
number of farms from which the milk supply of the average Amer- 
ican city is obtained, the liability of cases of typhoid fever occurring 
on these farms, and the numerous ways in which the infection may be 
conveyed from the patient to the milk. New York City’s milk supply, 
according to Darlington, is derived from 35,000 farms, and shipped 
from TOO creameries, located in 6 States. It is easy to appreciate Iioav 
difficult and expensive it would be to keep up a sufficiently thorough 
supervision of the multiple sources of that city’s milk supply. It is 
practicable to accomplish much toward the prevention of the infec- 
tion getting into the milk after the milk is delivered to the city. 
The following requirements are suggested: 
1. Location of the dairies in good surroundings. 
