Diseases of Domestic Animals in Nyasaland. 25 



a numerical expression of the virulence of the T. pecorum of Nyasaland. It 

 must he carefully noted that only fatal cases are taken into account. In 

 human medicine duration of disease means the number of days between the 

 beginning of the illness and recovery. Here it means the number of days 

 between infection and death. The table also shows against which animal 

 the energies of T. pecorum are chiefly directed. It is certain that it is only 

 by the detailed study of many strains of each of the African species of 

 trypanosomes that a satisfactory classification of this important group of 

 hsematozoa will be arrived at. This work must be done on the spot, 

 where the natural conditions for the normal life of the parasite are 

 present, and where frequent opportunity of passing through the invertebrate 

 host — the tsetse fly — exists. It is absurd to expect to arrive at any 

 classification at all approaching a true one by the study of strains of trypano- 

 somes kept for many years and undergoing many vicissitudes in our European 

 laboratories. 



Table XIX. — The Average Duration of Life, in clays, of Various Animals 



infected by T. pecorum. 





Donkey. 



Cattle. 



Goat. 



Pig. 



Monkey. 



Dog. 



Guinea-pig. 



White rat. 



Average duration, 

 in days 



87? 



121? 



*" '55 : 



21 



129 



48 



41 



33 



Number of animals 

 employed 



1 



4 



59 



1 



11 



57 



5 



10 



Table XX. — The Percentages of Eecoveries in Various Animals from 



T. pecorum Infection. 





Donkey. 



Cattle. 



Goat. 



Pig. 



Monkey. 



Dog. 



Guinea-pig. 



White rat. 



Percentages 



80 



35 



12 











1 











Number of animals 



5 



17 



70 



1 



11 



63 



5 



10 



employed 



















The Carrier of T. pecorum, ISTyasaland. 



In Nyasaland the carrier is G. morsitans, of which 4 - 6 per 1000 were found 

 infected by this species. This is the minimum, but the real proportion of 

 infected flies is probably three or four times as great. An account of the 

 development of T. pecorum in this tsetse fly will be dealt with in a future 

 paper. There is also some evidence derived from the outbreak among the 

 Mvera cattle that, given infected animals in a herd, it is possible that Tabanidce, 



