YELLOW FEVER INSTITUTE. 
Treasury Department, Bureau of Public Health and Marine-Hospital Service. 
WALTER WYMAN, Surgeon-General. 
Bulletin No. 14. 
Section B.—ETIOLOGY. 
P. A. Surg. M. J. ROSENAU, Chairman of Section. 
EXPERIMENTAL STUDIES IX YELLOW FEVER AND 
MALARIA. 
By M. J. Rosenau, Passed Assistant Surgeon, 
Herman B. Parker, Passed Assistant Surgeon, 
Edward Francis, Assistant Surgeon, 
George E. Beyer, Acting Assistant Surgeon. 
THE CAUSE OP YELLOW PEYER. 
The cause of yellow fever is not known, but we have to consider 
the Myxococcidium stegomyice of Parker, Beyer, and Pothier. 
These authors described in some detail the life cycle of a supposed 
animal parasite in infected mosquitoes closely resembling coccidia. 
It was our first duty to investigate the merits of this announcement. 
We therefore first sectioned about one hundred normal mosqui¬ 
toes, Stegomyia and Culex , both male and female. A study of these 
slides soon convinced us that bodies resembling Myxococcidium stcgo- 
myiae may be found in normal mosquitoes and that for the most part 
these bodies were yeast cells in various stages of reproduction. Car- 
roll had called our attention to this in a conversation and subsequently 
discussed it in an article published in the Journal of the American 
Medical Association for November 28, 1903. 
Since then the French commission, working at Rio de Janeiro,® 
has come to the same conclusion. 
a Marehoux, Salimbeni, and Simond: La fievre jaune; rapport de la mission 
frangaise. Ann. de Inst. Pasteur, tome XVII, November, 1903. 
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