DISEASE SPREAD BY COMMERCE 309 



organism known as Nuttallia equi, which seems to 

 combine both the features of Babesia and Theileria. 



Intercommunication between different districts is 

 largely interrupted, then, by the loss of transport 

 animals, and nowhere is this more seen than in 

 districts in the tropics newly opened up to commerce 

 or to civilization. When there was little communi- 

 cation between the different tribes in Africa, certain 

 trade routes only were used, as experience had 

 shown that others, often more direct, were fatal to 

 cattle. The advent of the European official and 

 trader changed this. Their work took them into 

 the "bad" places, with the inevitable ill-effect on 

 their transport animals, and also increase in the 

 evil, since these animals were capable of passing on 

 the virus to tsetse and other flies in hitherto unin- 

 fected districts. Thus the trader has been said to 

 have laid a trail of disease from the coast to the 

 interior, and the problem of the development of 

 many parts of tropical Africa is intensified. 



Human beings, food animals, transport animals 

 all are alike affected by the presence of minute 

 Protozoa, and thus certain districts are almost 

 forbidden ground to white men. Yet overcrowding 

 is rampant in many cities of the Old World, and 

 room is needed for their surplus population. The 

 progress of manufactures demands many products 

 only obtainable from semitropical and tropical lands. 

 The food-supply is one of the most pressing neces- 

 sities of the present time. And, in contrast, immense 

 districts of the world are underpopulated, yet fertile 

 and richly productive, capable of supplying all the 



