169 



The authors siimniarise Iheir irsults as follows:-— 



1. TJie human trypauosonie (T . rhudesicn.sc) is dislributfd 

 widely througJiout South Central Africa. 



2. There is no essential difference between the clinical mani- 

 feslations of the disease in man caused by T. rhodcsicnsc and t!ial 

 due to T. (jambicnsc, except i)()ssil)ly the oivater virulenc- of tlie 

 former. 



3. T. r-hodesicnsc is transmitted in Khodesia by Glosaina 

 nioi'sitdHS. 



4. Approximately 8-5 per cent, of the Hies nuvy become per- 

 manently infected and capable of transmitting' the virus. 



5. The period which elapses between the infecting' feed of tlie 

 flies and the date on which they become infective varies from 

 eleven to twenty-five days in the Luangwa Valley. 



G. Attempts carried out at laboratory temperature on the 

 Congo-Zambesi plateau during' tlie cold season to transmit the 

 human trypanosome by means of (r. i/iorsitdiis were invariably un- 

 successful in spite of" the fact that G80 tlies were used in these 

 experiments. 



T. The developmental cycle of T. rJtodesiensem G. uiorsiftuis is to 

 a marked degree influenced by the temperature to which the Hies 

 are subjected. High temperatures (75-85° F.) favour the 

 development of the parasite, whilst low temperatures (GO°-TO° F.) 

 are unfavourable. 



8. The first portion of the developmental cycle can proceed at 

 the lower temperatures, but for its completion the higher 

 temperatures are essential. 



9. The parasites may persist in the fiy at an incomplete stage 

 of their development for at least sixty days under unfavourable 

 climatic conditions. 



10. These observations aftord an adequate explanation of the 

 extremely long latent periods of trypanosomes in Glossina which 

 have occasionally been observed by various workers. 



11. The relative humidity of the atmosphere has apparently no 

 influence on the development of the trypanosome in G. morsifans. 



12. Mechanical transmission does not occur if a period of 

 twenty-four hours has elapsed since the infecting meal. 



13. G. morsitans, in nature, has been found to transmit the 

 human trypanosome. 



14. The chief reservoir of the human trypanosome is the 

 antelope. 



15. The results of examination for the human trypanosome of 

 the blood of a large number of monkeys, wild rats and mice were 

 invariably negative. 



In Section II. the same autliors discuss the trypanosomes of 

 game and domestic stock and say that in the Luangwa Valley 

 a great variety of game is found, but domestic stock is very scarce 

 and in some districts non-existent. K few goats are occasionally 

 found and there is some evidence to show that these animals under 

 natural conditions are not so insusceptible to trypanosomiasis as 

 is locally supposed. 



The natives recognise the impossibility of keeping dogs in 

 ily-infested areas. At Ngoa, on the Congo-Zambesi watershed, 



