274 Sir D. Bruce and others. Trypanosomes in [Jan. 13, 



This part of the country is situated in the proclaimed Sleeping-Sickness 

 Area of Nyasaland, which extends from the Chirua river (lat. 13° 20' S., 

 long. 34° E.) in the north to the Lintipe river (lat. 13° 50' S., long. 34° 30' E.) 

 in the south. It is bounded on the east by the Lake and on the west by the 

 foot-hills. The area is about 50 miles from north to south and 25 from east 

 to west. These figures are only approximate, as the available maps are far 

 from correct. This is the only part of this country in which cases of the 

 human trypanosome disease of Nyasaland, up to the present, have been 

 found. It will be seen, then, that these animals were procured from the 

 very heart of the Sleeping-Sickness Area. 



Among the 180 animals, 57 were found to harbour pathogenic try- 

 panosomes — 31*7 per cent. 



Table II gives the species of trypanosomes found in the 180 animals. 

 Here a difficulty is encountered — the classification. The tendency in this 

 branch of natural history, as in all others, is to multiply species. 



In a previous paper* the trypanosome causing human trypanosome 

 disease in Nyasaland was called Trypanosoma rhodesiense, on account of the 

 presence of posterior-nuclear forms. This trypanosome agreed in all other 

 respects with Trypanosoma brucei, the common trypanosome of wild animals 

 in South Africa, and the cause of the tsetse-fly disease, or Nagana. 

 In order to compare the two species of trypanosomes more closely, the Com- 

 mission procured, by the kindness of Dr. A. Theiler, C.M.G-., Pretoria, a strain 

 of Nagana from the same spot in Zululand where it was first discovered in 

 1894. Much to the surprise of the Commission it was found that T. brucei 

 has quite as large a proportion of posterior-nuclear forms as T. rhodesiense, and 

 that the blunt-ended character is common to both species. The Commission is 

 therefore driven to the conclusion that T. rhodesiense is neither more nor less 

 than T. brucei, and that the human trypanosome disease of Nyasaland is Nagana. 



To this it may be objected that Nagana has never been known to attack 

 human beings. This has probably been due to faulty diagnosis, cases in man 

 being returned as malaria. 



The pathogenic trypanosomes then, found in the blood of wild animals in 

 Nyasaland, up to the present, by the Commission are T. brucei (Plimmer 

 and Bradford) vel rhodesiense (Stephens and Fantham), T. pecorum, T. simice, 

 and T. caprce (Kleine). T. ingens is also found, but this trypanosome 

 cannot, with our present knowledge, be considered a pathogenic species to 

 man or domestic animals. 



In Table II the plus sign means that the trypanosome named at the top 

 of the column was present in the blood. The other plus signs signify that 

 * ' Eoy. Soc. Proc.,' 1912, B, vol. 85, p. 423. 



