18 



TYPHOID FEVER. 



It is not the writer's intention to go further into the causation of 

 this disease than he has already done in his introductory remarks. 

 He wishes, however, to point out as forcibly as possible the danger 

 of its spread by insects and the methods of avoiding this danger. 



House flies and breeding places. — The principal insect agent in this 

 spread is the common house fly (fig. 9), and this insect is especially 

 abundant in country houses in the vicinity of stables in which horses 

 are kept. The reason for this is that 

 the preferred food of the larvae of 

 house flies is horse manure. House 

 flies breed in incredible numbers in 

 a manure pile largely derived from 

 horses. Twelve hundred house flies, 

 and perhaps more, will issue from a 

 pound of horse manure. Ten days 

 completes a generation of house flies 

 in the summer. The number of eggs 

 laid by each female fly averages 120. 

 Thus, under favorable conditions, the 

 off'spring of a single over-wintering 

 house fly may in the course of a 

 summer reach a figure almost beyond 

 belief. With an uncared-for pile of 

 horse manure in the vicinity of a 

 house, therefore, flies are sure to 

 swarm. Their number practically 

 will be limited only by breeding op- 

 portunities. They are attracted to, 

 and will lay their eggs in, human 

 excrement. Under favorable condi- 

 tions they will breed, to some extent, 

 in this excrement. They swarm in 

 kitchens and dining rooms where 

 food supplies are exposed. They are 

 found commonly in box privies, which sometimes are not distant 

 from the kitchens and dining rooms. Therefore, with an abundance 

 of flies, with a box privy near by, or with excremental deposits 

 in the neighborhood, and with a perhaps unsuspected or not 

 yet fully developed case of typhoid in the immediate neighborhood, 

 there is no reason why, through the agency of contaminated flies 

 alighting upon food supplies the disease should not be spread to 

 healthy individuals. That it is so spread is not to be questioned. 

 That under the unusual conditions of the army concentration camps 



155 



Fig. 6. — Full-grown larva of Culex. 

 Enlarged (author's Illustration). 



