YELLOW FEVER : POSSIBLE GERM 169 



the insect. Knowingly, and deliberately, these 

 American investigators in Cuba allowed Stegomyia 

 that had fed on yellow fever patients to bite them. 

 They observed closely all that followed in their own 

 cases until unconsciousness prevented further observa- 

 tions, and the sacrifice of life itself proved the point 

 at issue, and opened the way for the salvation of the 

 enfevered parts of the world. 



What does S. fasciata carry and transfer to man ? 

 That, as before indicated, is a moot point. Until 

 four years ago few indications of a parasite had been 

 found ; the virus was able to pass through a filter, 

 and hence anything present must be extraordinarily 

 minute. Dr. Seidelin has found certain bodies both 

 in the blood-corpuscles and in the tissues of yellow 

 fever patients. The structures are very minute. 

 They have ringlike, oval, or sometimes irregular 

 forms, and seem to consist of a small amount of 

 cytoplasm with a little deep - staining (nuclear) 

 material, judging from stained specimens. The 

 bodies in question somewhat resemble very young 

 malarial parasites and the organism, Theileria parva, 

 of East Coast fever in cattle. They are smaller than 

 Babesia (see Chapter IX.). 



Although yellow fever in its acute form is recog- 

 nized with a considerable amount of certainty, yet 

 at its commencement, as with most disorders, there 

 are few symptoms. Chill and cold, with headache, 

 are usual. Pains in the back and limbs may be 

 present. The temperature rises for twenty-four to 

 forty-eighty hours, and may even reach 105 F., and 

 this continues for four to five days, the pulse also 



