100 
The infective principle of yellow fever may pass the pores of a 
Pasteur-Chamberland B filter. 8 
Particles of carbon Ausible with Zeiss lenses pass through both the 
Ber kef eld 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 1 1 
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 tAvo hours; but when the disease 
is transmitted by such artificial means as the inoculation of blood or 
blood serum the period of incubation shoAvs 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, 
feA^er, 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 internals; 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 tAvo pounds per 1,000 cubic 
feet with an exposure of tAvo hours is sufficient to kill Stegomyia 
