174 THE MFUMBIRO VOLCANOES 



almost wholly a water-side people, who live entirely 

 by fishing. At the south-east corner of the lake 

 are some curious colonies of lake-dwellers whose 

 huts are built several yards from the shore, with the 

 object, presumably, of escaping the attack of the 

 lions, which are always in attendance on large herds 

 of game. At Vichumbi, a small village at the 

 extreme south end of the lake, our camp was sur- 

 rounded by a high reed -fence for the same purpose, 

 and only a few days before we arrived there a man, 

 who incautiously went outside the fence after dark, 

 had been carried off and eaten. 



We had intended to stop for a few days at 

 Vichumbi to shoot some antelopes and visit the 

 villages of the lake- dwellers, but in that we had 

 reckoned without the spirillum.* There is a species 

 of tick {Ornithodoros moubatd), a frequenter of 

 native houses and old camping-places, which carries 

 in its blood a micro-organism called Spirochceta 

 duttoni. When it is introduced into the blood of 

 a man by the bite of one of these ticks, the spiro- 

 chaeta is the cause of a particularly unpleasant 

 relapsing fever. An ordinary attack lasts for two 

 or three days, and recurs again after an interval of 

 a week or more ; in severe cases the attacks may 

 be continued for months. Hitherto no satisfactory 

 remedy has been discovered for the fever, and all 

 that can be done is to take steps to avoid being 

 bitten by the tick. There are some districts in 

 * See Appendix. 



