THE COLON, TYPHOID AND DYSENTERY BACILLI 335 



suffer from typhoid fever, while others are merely healthy carriers 

 of the infection. From them as centers the bacilli are distributed 

 by contact and by intermediate objects. B. typhosus is able to 

 live for a considerable time in the external world, probably for 

 one to three weeks in ordinary surface waters and longer in soil. 

 It is able to grow and multiply in some foods, especially milk. 

 Water supplies contaminated with feces and urine from patients 

 or from healthy carriers have unquestionably been an important 

 factor in the causation of typhoid fever in the past, and the pro- 

 vision of a supply of drinking water free from all suspicion of 

 recent mixture with sewage is the first step in the control of this 

 disease in a community. The infected oyster from a sewage- 

 polluted oyster bed is another source of typhoid fever. The 

 contamination of food by permanent carriers of the bacilli is 

 difficult to control. All possible means need to be employed to 

 prevent these persons from handling foods prepared for consump- 

 tion, and especially milk. Flies (Musca domestica) are important 

 aids in the transfer of bacilli from discharges containing them, 

 especially from open privies, to foods exposed for sale or being 

 prepared in neighboring unscreened kitchens, i i 



The prevention of typhoid fever by restricting the distribu- 

 tion of the bacilli has been only partially successful in civil life 

 and in armies on a war footing it has proven wholly ineffective. 

 Vaccination to prevent typhoid fever was first extensively prac- 

 tised by Wright in the British army. Russell 1 following the method 

 developed by Wright and Leishman has prepared a vaccine with 

 which practically the whole U. S. army has been inoculated. 

 The vaccine is a suspension of B. typhosus in salt solution, stand- 

 ardized by microscopic count of the bacterial cells, sterilized by 

 heating at 53 to 56 for an hour and preserved by the addition 

 of 0.25 per cent trikersol. Three injections are given subcutane- 

 ously at intervals of 10 days, 500 million bacilli at the first dose 

 and 1000 million at each of the following doses. The results 



1 Russell: Boston Med. and Surg. Journ., 1911, Vol. CLXIV, pp. 1-8; Harvey 

 Lecture, 1913. 



