130 Insects and Disease 



1. The virus of the yellow fever is in the blood- 

 plasma, not in the corpuscles, for these may be re- 

 moved and the plasma still be infective. 



2. The virus is conveyed from one patient to an- 

 other by the yellow fever mosquito, Stegomyia 

 calopus, and in no other way except by experi- 

 mental injections. 



3. The patient is a source of infection only dur- 

 ing the first three or four days of the disease (this 

 after the three to six days of incubation). 



4. The virus must undergo an incubation period 

 of twelve to fourteen days in the mosquito before 

 she is capable of transmitting the disease. 



5. The parasite, whatever it is, has never been 

 seen. It is probably too small to be seen by any 

 of our present microscopes, even the recently in- 

 vented ultramicroscope. It is probably not a bac- 

 terial parasite but very likely a Protozoan, and cer- 

 tain specialists have even shown by the study of 

 all the available data that it almost certainly be- 

 longs to the Sporozoan genus Spirochete 



Now what does all this mean? It means the 

 saving of hundreds of human lives annually. It 

 means the banishing from many localities and 

 possibly very soon from the face of the earth of a 

 disease that since the earliest settlements on this 

 continent has been a source of terror. It means 



