546 APPENDIX 



How long do infected mosquitoes remain dangerous to the non-immune 

 community? This question cannot be definitely answered at present; 

 there is good presumptive evidence that the mosquito may harbor the 

 parasite through the winter and be enabled to transmit in the spring an 

 infection acquired in the fall. There is reason to believe that the mos- 

 quito, once infective, can transmit the disease at any time during the 

 balance of its life. 



With regard to the parasite itself, we cannot as yet say much. Number- 

 less dissections of infected insects have been made, and serial stained 

 sections have been prepared at various periods. The latter have led us 

 to expect something tangible in the near future, though until now nothing 

 definite has been discovered. . 



The question whether other genera of the Culicidce or other species 

 of Stegomyia are capable of transmitting yellow fever is still open for 

 discussion. It is best not to forget that such a thing is possible, though 

 the general opinion seems to be that yellow fever is restricted for its 

 propagation to the genus Stegomyia. 



