674 INFECTION AND IMMUNITY. 



the latitudes 15' North and 15' South, it is now 

 found one thousand miles up the Congo (Bangola, 

 Stanley Falls) and in East-central Africa on the 

 shores of the Victoria Nyanza Lake. "Now it ex- 

 tends from the mouth of the Katonga Kiver 

 through Uganda (1901, Cook), Kome Island, 

 Busaga, Buvuma, Kavirondo, Kisumu, Lumbwa, 

 Homa, Kasagunga, Lusinga Island, the eastern 

 shores of the lake, joining the south of the bound- 

 ary river Gori in the Udemi district of the Sultina 

 of Obo" (Kuata). 



occurrence. Its extension supposedly has been facilitated by 

 rapid transit. "The disease is most prevalent 

 amongst the inhabitants of low-lying shambas (ba- 

 nana and potato plantations) in places along the 

 shores of the Victoria Nyanza, or in wooded dis- 

 tricts not far from the water" (Christy). Those 

 living on high ground are much less infected than 

 those living in the low moist places near water. A 

 great deal of stress is laid on its close association 

 with inland bodies of water. 



It apparently has no relation to sex, age, sea- 

 sons, food or drinking water, and is related to oc- 

 cupation only in so far as the occupation carries 

 one into the low places mentioned. 



At one time (1891) Manson advanced the idea 

 that sleeping sickness is caused by the minute 

 sickness, pifaffa p ers t ans . it has since developed that this 

 parasite occurs in 70 per cent, of the natives in 

 certain districts, and that sleeping sickness may 

 occur in areas in which Filaria perstans does not 

 exist; Manson has abandoned this view. A num- 

 ber of investigators also found cocci in the cerebro- 

 spinal fluid, but this occurred very rarely during 

 life and at a late stage of the disease ; such organ- 



