164 SOME MINUTE ANIMAL PARASITES 



fever is but a mild form of " yellow jack," and needs 

 the same consideration. Biliary fever, bilious re- 

 mittent fever, and pernicious remittent fever all have 

 been used to cloak the name of the fatal malady 

 known to early medical colonial history as the 

 " Bulim fever," the " fever of Fernando Po," and 

 " the fever of the Bight of Benin." 



Disease is said proverbially to follow trade routes, 

 and the opening up of communication with the 

 interior of a country has a like result. Such is true 

 of yellow fever, and the best example probably is 

 afforded by West Africa, where the malady has been 

 reported from practically every town along the coast 

 and is now known in the interior along the courses 

 of the Senegal and the Niger, though in but few 

 cases. The Senegal cases practically follow the 

 railroad and the trade routes. The most thickly 

 populated area of West Africa is Sierra Leone, and 

 the Gold Coast is next to it in population so far as 

 the coast strip is concerned. Many attempts have 

 been made in Africa to fix the responsibility for the 

 spread of yelldw fever on one or other of these 

 places. Probably no one place is really responsible ; 

 it is more likely that the whole coast from Senegal 

 to the Cameroons is equally involved. 



There is one remarkable fact about yellow fever 

 which is in strong contrast with many tropical dis- 

 eases. The parasite of malaria was known long before 

 its carrier. The organism Trypanosoma gambiense was 

 known in some detail before Glossina palpalis was 

 incriminated. The Kala-azar Protozoon is well 

 known, while its carrier is still not perfectly demon- 



