Mabch 9, 1906.] 



SCIENCE. 



377 



We should not relax our constant watch- 

 fulness during the season of danger, but 

 we must realize that knowledge of the 

 existence of first eases requires a combina- 

 tion of factors not always obtainable and 

 not within our practical control. 



Destruction of Stegomyia. — Finally, we 

 must, I think, conclude that the destruction 

 of the only natural transmitting medium 

 is the surest preventive of yellow fever. 

 This measure also is subject, of course, to 

 imperfect application in practise, and in- 

 complete results. It is not sufficient, alone, 

 to guarantee against infection, but it offers 

 the important element of time during which 

 to encourage its thorough application; and 

 in the event of the failure of quarantine 

 and of the prompt recognition of infection, 

 the spread of the disease is modified by 

 even a partial destruction of the conveying 

 medium, and this gives time for perfecting 

 organization against the infected insects. 



The health authorities of this city were 

 convinced of the truth and importance of 

 the mosquito doctrine of yellow-fever con- 

 veyance upon its first announcement, and 

 of the importance of mosquito destruction. 

 Twice a law such as is now operative was 

 proposed and rejected, and our belief is 

 now, as it was then, that the destruction of 

 Stegomyia mosquitoes prior to the intro- 

 duction of yellow fever is the ounce of pre- 

 vention that is better than the pound of 

 cure. 



I show three charts of mortality for three 

 separate years, one of which, 1905, is a 

 yellow-fever year. 



The causes of death are those under 

 which yellow fever may be concealed, in- 

 tentionally or not. 



A careful analysis of these records does 

 not bear out the notion, expressed by some, 

 that yellow fever should have been recog- 

 nized earlier than the middle of July 

 through an inspection of the mortality 

 from these causes. 



The value of mortality charts is historic, 

 not prophetic, in respect to yellow fever. 



Investigation of individual cases, whose 

 circumstances, together with the given 

 cause of death, excite suspicion, is more 

 reliable than an observance of increase in 

 numbers, and is earlier available. This is 



