XXVI 



FLIES AND SLEEPING SICKNESS 



323 



or nose, and examined under tlic niieroseope, tlie minute; 

 wriggling parasite will be seen in the field. Careful 

 observations also show that though the parasites swarm 

 in the blood this is not their only, or, indeed their chief, 

 habitat, but they occur in the lymph glands and the 

 cerebro-spinal Huid. It was in this fluid that Castellani 

 discovered them and laid the real foundations of our 

 knowledge of the pathology of sleeping si(;kness. The 

 chief lesions which lead to the fatal termination of 

 trypanosomiasis and which secured for it the name 



Trj'panosomes (highly magnified). 



sleeping sickness are associated with the membranes and 

 superficial strata of the brain and spinal cord. For 

 these facts we are indebted to the careful work of Mott. 

 Having discovered that sleeping sickness was caused 

 by trypanosomes, the next and most obvious step was to 

 find out how the parasites obtained access to the bodies 

 of men and women. It has already been mentioned 

 that the early exploration of the interior of Africa was 

 seriously hampered by the fact that transport animals 

 acquired a disease due to the bite of a fly which was 

 particularly fatal to horses, donkeys, and dogs. Bruce 



Y 2 



