3 so SPECIFIC , m;cro-organisms 



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

 polluted oyster bed is another source of typhoid fever. Tht 

 contamination of food by permanent carriers of the bacilli is 

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

 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. 



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,^ 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 couni; of the bacterial cells, steriUzed 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 miUion bacilH at the first dose 

 and idoo miUion at each of the following doses. The results 

 in the U. S. army have been remarkably good, rivaling those 

 obtained with the use of vaccinia in the prevention of small- 

 pox. 



Experience has shown, however, that the immunity conferred 

 in this way is not always adequate to prevent the occurrence 

 of typhoid fever. A considerable number, in the aggregate, of 

 cases of bacteriologically proved typhoid fever occurred in the 

 American Expeditionary Forces in France in 19 18 and 19,19 and 

 in a few instances definite outbreaks of the disease occurred, such 

 that they might be termed small epidemics. Nevertheless it 

 may justly be concluded that typhoid vaccination has relegated 



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

 Lecture, 1913. • 



