366 
little alteration in virulence has been observed after a year’s passage 
through these animals. The two rats infected directly from the 
patient died in six and twelve days, respectively. The average 
duration of the disease in the first ten passages was 17 5 days, and 
in the last ten, 20 days. Incubation period, one to seven days; 
average four days. Duration, six to forty-five days; average 
nineteen days. 
T. gambiense. Fifty-four experiments. Incubation period, two 
to ten days; average four days. Duration, six to twenty-nine days; 
average fourteen days. 
•With a view to comparing the animal reactions of the Rhodesian 
Trypanosome with those of T. gambiense , the above results, and 
those obtained by other workers* with various strains of human 
trypanosomes, are summarised in Table 12. 
It is evident that the Rhodesian trypanosome differs very 
markedly from T. gambiense in its pathogenicity for various species 
of animals. In monkeys ( Macacus rhesus , Cercopithecus callUrickus 
and Cercopithecus ruber), dogs, rats and mice the disease runs a 
very acute course. Large numbers of trypanosomes were usually 
present in the blood. Rabbits, guinea-pigs and goats were easily 
infected, and died in a much shorter time than animals of the same 
species infected with T. gambiense , and parasites were much more 
constantly found in the blood and in greater numbers. Two 
donkeys and a horse quickly succumbed to the disease, try'panosomes 
being regularly observed in the peripheral circulation. 
These results show that in so far as virulence is concerned the 
parasite is widely different from T. gambiense —in fact it more 
closely resembles T. brucei in this respect than T. gambiense —and 
support the view advanced by Stephens and Fantham, on 
morphological grounds, that we have in ‘ T. rhodesiense’ a new 
species. 
Reports of the Sleeping Sickness Commission of the Royal Society. 
Thomas and Linton. Loc. cil. 
Lavcran. Loc. cit. 
Brumpt et Wurtz. 1 Maladic du Sommeil experimentale chez les Souris, Rats. Cobayes. 
Comptes Rendus Soc. Biologie, T. LVI, p. 567, 1904. 
Beck ‘ Expcrimentelle Beitrage zur Infektion mit Trypanosoma gambiense,' Arbeiten a. 
Ka,serl - Gesundheitsamte, S. 318, 1910. 
Bentmann und Gunther. Loc. cit. 
