Parasitism and Disease 



7 



advent of white men into this region and the conse- 

 quent migration of the natives along the trade 

 routes this parasite, which is the cause of sleeping 

 sickness, is being introduced into new regions and 

 thousands upon thousands of people are dying as a 

 result of its ravages. 



DISEASES CAUSED BY PARASITES 



Some two hundred years ago, after it became 

 known that minute animal parasites were associ- 

 ated with certain diseases and were the cause of 

 them, it rapidly came to be believed that all our ills 

 were in some way caused by such parasites, known 

 or unknown. Further study and investigation 

 failed to reveal the intruders in many instances 

 and so it began to be doubted whether after all 

 they were responsible for much that had been laid 

 at their doors. Then after it was discovered that 

 minute plant parasites, bacteria, were responsible 

 for many diseases they in turn began to be accused 

 of being the cause of most of the ills that the flesh 

 is heir to. 



In later years we have come to adopt what seems 

 to be a more reasonable view, for we can see and 

 definitely prove that neither of these extreme views 

 was correct but that there was much truth in each 

 of them. To-day we recognize that certain diseases, 



