214 DISEASES DUE TO BACTERIA 



(3) Uncooked vegetables grown on infected soils. 



(4) Shell-fish groAvn on polluted beds. 



(5) Direct contact with the soiled linen, stools and urine, typhoid 

 abscesses of the patient. 



(6) Contaminated soil resulting from defective drains and cess- 

 pools. The soil may be dry and be blown on to food or 

 swallowed in the dust. 



(7) Typhoid carriers. 



(1) F^CAL CARRIERS. 



The proportion of female carriers to the male is as five to one. 



As women have gall-stones more frequently than men, and as the 

 gall bladder is a habitat of the typhoid bacillus it is not tO' be wondered 

 at that symptoms of gall-stones occur in 14 per cent, of cases after 

 enteric fever. The bacilli may be passed down the gall bladder to the 

 intestines and expelled in the faeces without the patient being 

 obviously ill, yet such bacilli may be very virulent and cause death to 

 persons infected by them. The discharge of the bacilli appears to be 

 intermittent. It is stated that women are more commonly carriers 

 than men because their resisting powers are reduced by the decrease 

 in the alexins of the blood during the menstrual and puerperal periods. 



(2) FLY CARRIERS. 



Infection by the house-fly (Musca domestica) and the fruit-fly 

 (Drosophila ampelaphila) is most important because the fly takes up 

 the bacilli into the alimentary canal in which the bacilli increase in 

 number and virulence. (See habitats of house-fly, &c., p. 224.) 



The fly is a known foul feeder. After settling on fcecal material it 

 goes on to human food, regurgitates a little fluid from its crop to 

 dissolve the food substances and thus infects them. It also defc-ecates 

 frequently. The term "autumnal fever" has been given to epidemics 

 which are in the time of the greatest prevalence of the flies. 



(3) URINARY CARRIERS. 



In such cases the habitat is the renal pelvis which is usually 

 chronically inflamed. It may also live in the urinary bladder and 

 other processes of the urinary tract. The bacilli pass directly into the 

 urinary stream and are thus excreted. 



F^cal and urinary carriers may infect directly the air, food, food 

 utensils, drinking water and fomites, which in turn infect the victim. 



B. paratyphosus B, commonly met with in luirope, lives often in 

 the gall bladder and infects the faeces. It has not been found in the 

 urine. It has been found in the common house-fly. 



