1264 ' THE AFRICAN TRYPANOSOMIASES 



recognized for a long time. It appears also to be spreading north- 

 wards from Uganda, for Greig, in 1904, found it at Wadelai, on the 

 Victoria Nile, but not as high as Nimuli. It invaded the Lado 

 earlier than 1908, and in 1909 the disease was recognized definitely 

 in the Bahr-el-Ghazal Province of the Sudan. 



Therefore the distribution of the disease at the present time may 

 be said to extend along the West Coast of Africa, from St. Louis, in 

 Senegal, to Mossamedes, in Angola; from the coast to Timbuktu 

 on the Niger; through the whole of the Congo into Uganda and 

 Rhodesia ; from Uganda and Busoga southwards to late German East 

 Africa; and northwards into the Bahr-el-Ghazal Province. The 

 discovery of the tsetse-fly in Arabia makes it possible that the 

 disease may some day still farther 

 extend its area. 



There does not appear to be 

 any seasonal influence. 



etiology. — ^From the present 

 state of our knowledge it would 



Fig. 638. — ^Trypanosoma in 



Cerebro-spinal Fluid. p^^.. 638A.— Lymphocytic Accumu- 



Preparation from the cerebro-spinal lation around a Vessel in the 



fluid of a case of sleeping sickness. Brain. 



appear that from a clinical and aetiological point of view there are 

 three types of sleeping sickness, which may be differentiated as 

 follows: — 



I. The Equatorial type, caused by Castellanella castellanii and 



spread by Glossina palpalis. 

 II. The Southern type, caused by Castellanella rhodesiensis 



and spread by Glossina morsitans. 

 III. The North-Western type, caused by Castellanella gambiensis 

 (synonym, C. nigeriensis) and spread by some as yet 

 not clearly differentiated tsetse-fly, which may or may 

 not be Glossina palpalis, and which Dutton suggested 

 might possibly heG. tachinoides. 



For description of the parasites, see p. 417. 



Duke's researches made it possible that there is a vertebrate 

 reservoir for C. castellanii in the antelope, because he found a 

 trypanosome very like this organism in these animals, and because 



