TRYPANOSOMIASES OF RHODESIA. I^Q 



the Tr. bntcci encountered in Zululand in 1894 and in<4L'ganda, 

 1901). and indeed, I^ruce asks whether it is not possible that 

 Button and Todd's original Tr. dunorphon may not have really 

 'been Tr. bntcci. At the risk of labouring the point, it may be 

 recalled that when Theiler sent horses into the old area at one 

 time infected ^vith Tr. briLcci, they became infected with a try- 

 panosome of dimorphic type. There is no doubt also but that the 

 type of animal trypanosomiasis in certain parts of Rhodesia has 

 changed. Old hands have told me of the acute .syniiptoms which 

 rapidly followed the exposure of horses, donkeys, mules and 

 cattle to the bite of the " tsetse fly " in the Hartley district. 

 ]\Ien from Natal could not draw any distinction between the 

 disease as it was in 1892 to 1896 from that of which they had 

 had experience in the Delagoa Bay districts. At the present 

 time quite a high percentage of oxen sufifer from a very mild 

 'infection from which they recover, and equines appear to be 

 immune. May it not be that with the arrival of civilisation the 

 trypanosome, attenuated by constant passage through wild ani- 

 mals, become exalted in virulence in new and highly susceptible 

 hosts, in which, again, by acclimatisation it has once more become 

 attenuated? 



This discussion may also be extended into the study of the 

 human trypanosomiasis of Rhodesia and Nyasaland. Two ob- 

 servers, Stephens and Fanthan, have drawn attention to the 

 peculiar morphology of a trypanosome in a case of sleeping 

 sickness from this country. I may say that their strain • was 

 obtained from an European. W. A., who apparently contracted 

 the disease in the Luangwa \'alley or some other part of North- 

 East Rhodesia. This patient arrived in Hartley, and his blood 

 was brought to me hy Dr. jMackenzie for examination. Trypano- 

 somes were found in it, and, by the courtesy of Dr. Heygate 

 Ellis, I secured a quantity of virus and originated a strain of 

 the trypanosomiasis, which 1 have ibeen carefully studying since 

 November, ic;o9. During this period I have not encountered the 

 phenomenon described by Stephen and F'anthan, namely, that 

 among the short and stumpy forms some have the nucleus at 

 the posterior (non-flagellated) end. I certainly have seen dis- 

 torted forms of the parasite, which have become altered in such 

 a way that the nucleus has appeared posterior to the centrosome, 

 but these might have been artifacts. 



I did not feel justified in announcing the discovery of a 

 new species. The necessity for care in such a diagnosis is 

 obvious ; for, if we have in Rhodesia to deal with a new try- 

 panosomiasis, due to a species of trypanosome concerning which 

 we know nothing, our difificulties are the greater since there is 

 no guarantee that the old and tried methods of prophylaxis will 

 be of avail in arresting the spread of the disease. 



Thus we see how important is the study of morphology, and 

 yet how dangerous is the dogmatic dififerentiation of species by 

 morphological features alone. For it must be remembered that 



