128 TYPHOID FEVER 



' carriers,' and of unrecognized, incipiently mild, atypical and 

 typical cases of typhoid. Morgan and Harvey (1909) made 

 some very interesting observations on the persistence of 

 B. typhosus in the urine and faeces of a typhoid carrier. The 

 bacilli could be cultivated from a patch of ground exposed to 

 bright sun six hours after a typhoid carrier had voided urine on 

 it. In the corner of a dark hut the bacilli were present in large 

 numbers for five hours and in smaller numbers up to thirty hours. 

 Faeces were passed into a ' gumlah ' half filled with dry earth 

 and then covered with dry earth. B. typJiosiis was isolated from 

 the surface of the faecal deposit on the seventh day and could 

 be recovered from the interior up to eighteen days. From a 

 sample of blanketing soiled with liquid fsces B. typhosus was 

 isolated up to the fortieth day, but not later. 



In properly sewered towns these discharges are disposed of 

 without flies being able to gain access to them, except in dirty 

 and ill-kept courts and alleys, and consequently in such towns 

 flies probably play an insignificant part in the spread of the 

 disease. In towns and villages with privies and privy-middens 

 the flies have greater opportunities of infecting themselves, and 

 further research will probably show that under these conditions 

 they may be factors in the spread of the disease. In towns and 

 military camps where the night-soil is buried in inefficiently 

 constructed trenches, they appear to play a most important part 

 in the spread of the disease as will be shown later. 



Even when infected flies are found it is difficult to state 

 definitely the exact means by which infection has been carried 

 to the individual. The probability is that food is the medium 

 through which the specific organisms reach the person infected ; 

 and the article of food which off'ers the best medium for 

 the growth and multiplication of the bacilli is milk. The 

 chief difficulty in tracing the exact channel of infection in a 

 series of cases of this disease is that the incubation period is 

 long, i.e. in most cases over ten days, so that investigations 

 cannot be commenced for at least a fortnight after actual 

 infection has taken place. After this time there will be no 

 remains of the food which has been the actual means of infection, 

 and unless the contamination of food continues to take place it 



