100 



The infective principle of yellow fever may pass the pores of a 

 Pasteur-Chamberland B filter. 



Particles of carbon visible with Zeiss lenses pass through both the 

 Berkefeld and Pasteur-Chamberland B filters. 



Because the virus of an infectious disease passes a Berkefeld or 

 Pasteur-Chamberland B filter it does not necessarily follow that the 

 parasite which passed the filter is " ultramicroscopic," or that it may 

 not have elsewhere another phase in its life cycle of large size. 



The filtration of viruses may succeed or fail, depending upon the 

 character of the filter, the diluting fluid, the pressure, time, tempera- 

 ture, motility of the particles, and other factors. 



The period of incubation of yellow fever caused by the bites of 

 infected mosquitoes is usually three days, sometimes five days, and in 

 one authentic instance six days and two hours; but when the disease 

 is transmitted by such artificial means as the inoculation of blood or 

 blood serum the period of incubation shows less regularity. 



Yellow fever may be conveyed to a nonimmune by the bite of an 

 infected Stegomyia fasciata; but the bites of Stegomyia which have 

 previously (over twelve days) bitten cases of yellow fever do not 

 always convey the disease. 



Fomites play no part in the transmission of the disease. 



The tertian and estivo-autumnal malarial parasites will not pass 

 the pores of a Berkefeld filter. 



We have demonstrated a poison in the blood during the chill of ter- 

 tian infection which, when injected into another man, caused chill, 

 fever, and sweating. This poison, while present in a case of tertian 

 during the rise of temperature, could not be demonstrated in the blood 

 of a case of estivo-autumnal fever during the decline of the paroxysm. 

 While this poison reproduced the symptoms of the disease, still the 

 data are too limited to consider it the malarial toxin. 



Stegomyia fasciata is a domestic insect. It is most active dur- 

 ing the day, but will bite at night under artificial light. The female 

 lays eggs at intervals; the maximum number of eggs laid by one 

 insect observed by us was 101. The mosquito does not always die 

 directly after ovipositing. 



Stegomyia fasciata may bite and draw blood from cadavers, 

 although the danger from spreading the infection from this source is 

 remote. 



Male and female Stegomyia fasciata may pass a screen containing 

 16 strands, or 15 meshes to the inch, but not one of 20 strands, or 19 

 meshes to the inch. 



Tobacco smoke produced by burning two pounds per 1,000 cubic 

 feet with an exposure of two hours is sufficient to kill Stegomyia 



