122 PRINCIPLES AND PRACTICE OF MILK HYGIENE 
become chronic bacilli carriers. The bacilli may also be 
carried by flies and be blown about in dust. 
The typhoid bacillus multiplies rapidly in milk and 
the number may be greatly increased in a short time. The 
milk is not changed in appearance. The organism grows 
in slightly sour milk; it is checked or destroyed by a high 
degree of acidity, but it survives the degree of acidity 
existing in cream ripe for churning. It may live in milk 
several days and may be present in fresh butter and new 
cheese. Bruck found virulent bacilli in butter after 
twenty-seven days. Typhoid bacilli in milk are destroyed 
when exposed to a temperature of 60° C. (140° F.) for 
two minutes (Rosenau). 
When an outbreak of typhoid fever occurs which has 
the characteristics of a milk-borne epidemic, the sus- 
pected milk supply should be stopped, or pasteurized 
under supervision, and an investigation made with the 
object of discovering and abolishing the source of the 
infection of the milk. Immediate medical attention to 
cases of illness affecting the dairyman, his employees, or 
members of their households, proper supervision of cases 
of typhoid fever by health authorities, the sterilization of 
milk bottles before refilling, and a pure water supply will 
greatly reduce the liability of the occurrence of such epi- 
demics. There is no method known which is entirely 
satisfactory in preventing the direct infection of milk by 
walking typhoid cases or by chronic bacilli carriers. 
Recently, some local health authorities have required that 
blood samples be taken from dairy employees and sub- 
mitted to the Widal test as a safeguard against chronic 
bacilli carriers; a few high-class dairies have been follow- 
ing this plan for some time. Several states have laws 
requiring dairymen to report to the local health author- 
