THE HOUSE FLY 31 



healthy ones in other parts, perchance a mile or more 

 distant. 



It must also be remembered that in a considerable per- 

 centage of cases of typhoid fever, the patient, for weeks 

 and even months after convalescence, and long after he 

 has returned to business, still excretes the typhoid germs 

 in both excrement and urine. There are also many people 

 who are attacked with typhoid fever in a mild form and 

 who are not sufficiently unwell to take to bed. Then again 

 there are individuals who are immune to typhoid fever, but 

 in whose systems the microbes live and thrive, making 

 them a constant danger to other people in the community. 

 -It will thus be seen that in spite of the most careful isola- 

 tion of a typhoid patient and the thorough disinfection of 

 all infected matter, this dreaded disease may, nevertheless, 

 be spread by those who have recently recovered from a bad 

 attack, and by examples such as the other two instances 

 cited. Therefore in the case of typhoid fever, nothing 

 short of the strictest sanitary precautions and the exter- 

 mination of the House Fly will eradicate the disease from a 

 community. 



When a case of enteric fever, otherwise known as typhoid, 

 occurs, the originating cause is usually attributed to some 

 defective drain, a manhole, orsluit, giving forth bad odours, 

 &c. These unpleasant odours do not infect people with 

 disease. The frequent breathing of air rendered impure 

 by foul gases will certainly lower the standard of health 

 and prepare the body for infection by disease germs, but 

 actual infection is not caused in this way. Most diseases 

 take several days, sometimes as many as ten and more, to 

 incubate, and in the interval the victim is unaware that in 



