436 INFECTION AND IMMUNITY. 



Park estimates that from 2 to 5 per cent, of all 

 people who recover from typhoid, continue to 

 excrete typhoid bacilli by way of the urinary or 

 alimentary tracts. Park also estimates that one 

 out of every 500 adults who have never had 

 typhoid, harbor typhoid bacilli. The bile is gen- 

 erally regarded as the medium in which the bacilli 

 perpetuate themselves in the case of the carriers. 



By whatever means an apidemic is set in motion 

 primarily, it is usually aggravated and prolonged 

 by the occurrence of contact infections (indirect 

 contact). The hands of the nurse, physician, or 

 others who come in contact with the patient be- 

 come contaminated from the stools, urine, soiled 

 linen or skin of the patient, and the organisms 

 subsequently are transferred to food, drinking 

 water, or in other accidental ways reach the mouth. 

 Each new case is a fresh focus from which infec- 

 tion may be carried to others, and the chances of 

 milk and food infection become greater as the 

 cases multiply. When the discharges are not dis- 

 infected or are improperly disposed of, soil or 

 house infection may occur and the possibility 

 of transmission by germ-laden dust becomes of 

 importance. Dust infection from dried urine 

 or feces and drop infection from urine, water, 

 or the sputum of the patient are theoretical- 

 ly possible, but would seem to be of minor sig- 

 nificance. That flies may carry the organisms 

 from open vaults or cesspools and deposit them on 

 food or in drinking water has been appreciated 

 in epidemics in military camps .and elsewhere. 

 Typhoid bacilli have been cultivated from flies 

 which were taken from the vicinity of infected 

 material. 



