664 SCIENCE PROGRESS 



i. The patients develop sleeping sickness, or die of 

 pneumonia or some other intercurrent affection. 



2. They remain in good health for a long period, and seem 

 to develop a tolerance for the trypanosome. 



The question is whether any of these acquire sufficient 

 immunity to destroy the parasite, and whether this immunity 

 can in any way be artificially increased. 



A curious condition has been found in the stomach in cases 

 of sleeping sickness, there being areas with a dark-red centre 

 and light-red periphery, consisting of masses of petechial 

 haemorrhages. The lymphatic glands in all cases of sleeping 

 sickness are enlarged, and the juice taken by puncture during 

 life contains many active, and also numbers of disintegrating 

 trypanosomes. In the cerebro-spinal fluid taken during life 

 are found lymphocyte cells, occurring in greater numbers the 

 more advanced the case. In a certain proportion of cases in 

 the last stage, the gland juice becomes infected with bacteria, 

 especially diplostreptococci. 



From the investigations made, it is now clear that all the 

 essential features found in trypanosome or trypanosoma fever 

 are found in sleeping sickness, that many of the cases end 

 fatally as sleeping sickness, that a certain number die of inter- 

 current affections, especially pneumonia, and that a certain 

 proportion show a considerable degree of tolerance to the 

 parasite. Apparently some of the last class of cases develop 

 sufficient resistance to destroy the trypanosoma. 



As regards the habits of Glossina palpalis, which carries the 

 infection of sleeping sickness, it has been found : 



i. That this fly abounds where there are trees and bushes 

 near water, and that sleeping sickness occurs in these places. 



2. That sleeping sickness has spread from Uganda and 

 Usoga east and south. 



3. That there is no sleeping sickness east of a line drawn 

 from the Maragoli hills down the Maragoli stream to the bay, 

 and across the bay (Kavirondo) to Homa. This line is found 

 also to be the eastern limit of the tsetse fly, with the exception 

 of the Port Florence district. 



4. That the Kuja is the only river that carries the tsetse fly 

 inland, and is also the only river that has trees at its mouth 

 and thick vegetation along its course. 



From experiments on animals, it appears that the Glossina 



