164 AGRICULTURAL BACTERIOLOGY 



place, the bacilli usually disappear from the body, but in 

 about 4 per cent, of cases the organisms persist for a period 

 of time. Exceptional cases have been recorded in which 

 the organisms were eliminated for many years after re- 

 covery. Such people are known as typhoid carriers. It is 

 estimated that about one in each thousand cf the population 

 is to be classed as a typhoid carrier. Whenever such a 

 carrier is engaged in the preparation or handling of food, 

 an epidemic of typhoid may result. An outbreak of four 

 hundred cases in New York city was traced to a person who 

 had had the disease forty-seven years before. As has been 

 stated, the contamination of milk is important, due to the 

 opportunity for the growth of the bacilli ; but any food may 

 become contaminated and thus become the cause of trouble. 

 Since no one recognizes the typhoid carrier as such, and 

 since generally he does not even know his own condition, the 

 problem of protecting the public against this source of 

 typhoid fever seems to the modern health officer impossible 

 of solution. 



Oysters and typhoid fever. Shell-fish represent another 

 food that is not infrequently concerned in the spread of 

 typhoid fever. When oysters are removed from the salt 

 water in which they have grown, they are placed in fresh 

 water for a short period in order that they may be "fat- 

 tened" or "plumped" by the absorption of water. If the 

 water in which they are placed is polluted with sewage, the 

 oyster will be contaminated, and since they are often con- 

 sumed raw, opportunity is presented for the transmission of 

 the organism. 



The house-fly. Another agency in the distribution of 

 typhoid fever is the house-fly. If infectious material is 

 deposited where flies have access to it, they may carry the 

 organisms to the food with which they come in contact. 

 All privy vaults should be so constructed that flies can not 



