PREVENTIVE MEASURES 177 



Success will also to a great degree depend upon the 

 applicability of Doctor Hewitt's isolated observations 

 upon the period between issuance and sexual maturity 

 to other seasons and to other parts of the world. 



SCREENING 



Three years ago I made an attempt to estimate the 

 amount of money spent annually in screening houses 

 in the United States. As close an estimate as could 

 conscientiously be made seemed to indicate that more 

 than $10,000,000 are spent every year for this kind 

 of protection against flies and mosquitoes. In fly-rid- 

 den localities the expense is undoubtedly justified, since 

 the majority of the flies are kept out by careful screen- 

 ing. No system of screening, however, seems to be so 

 perfect as to keep them all out. They get in, one way 

 or another, in spite of care; even where double doors 

 are used they eventually gain entrance. In the summer 

 time, in country houses having large open fireplaces 

 disused during warm weather, flies undoubtedly come 

 down the chimney, and it is necessary under those con- 

 ditions to arrange a wire screen before the open fire- 

 place in such a way that it can easily be removed on a 

 cold day. 



The whole expense of screening, however, should be 

 an unnecessary one, just as efforts to destroy flies in 

 houses should be unnecessary. Their breeding should 

 be stopped to such an extent that all these things would 

 be useless. 



