46 THE FEVER CENSUS 



that suffered from fever of various kinds. In this 

 way the percentages of fever incidence can be ob- 

 tained. These percentages can be checked by the 

 figures obtained from the hospital and dispensaries. 

 If the inquiries have concerned a sufficient number of 

 persons, there will only be such a small statistical 

 error that it can be ignored ; but this error may always 

 be discovered by the Pearson-Poisson formula a 

 formula that is well known to all students of vital 

 statistics. 



But how is it possible to discover the exact nature 

 of the fevers that occur in the town ? How can it be 

 known that any of them are conveyed by mosquitos ? 

 It may be stated that this question cannot be answered 

 at once in the present state of knowledge. Fevers in 

 warm climates have not yet been completely classified. 

 The returns will include all sorts of fevers of various 

 origin. But if the figures obtained before the mos- 

 quito campaign begins are compared with those 

 obtained from the same sources and in precisely 

 the same way afterwards, when the mosquitos 

 have disappeared from the town, a difference will 

 be noticed a marked difference. If the campaign is 

 carried out properly, the mosquitos will disappear 

 rapidly ; but the fevers will disappear even more 

 rapidly. 



If there is no health officer, an official may be 

 appointed by the municipality or any local authority, 

 or even a community of residents, to undertake the 

 mosquito campaign, and to carry out the fever cen- 

 sus. A medical man is the best person to do this, of 



