32 Morphology of a Trypanosome of Sleeping Sickness, ete. 
Whether this be so or not, the condition is not parallel to the one under 
discussion, for the differences in 7. theilert are characteristic of all strains 
of this trypanosome, but the forms which we have described in this paper 
have, we believe, never been seen before in any strain of R. gambiense 10 man 
or animals. 
5. We are aware that parasitic flagellates may exhibit morphological varia- 
tions due to changes in metabolism or to differences in environment. 
However, this Rhodesian strain of trypanosome with posterior nucleus was 
seen in rats infected from the patient before he was treated with drugs. At 
first sight also it might appear that the posterior nucleus denoted merely 
approaching division or even assumption of the round form. However, we 
have seen division of these posterior nuclear forms (fig. 12). In any case the 
pecuhar morphological feature exhibited by the Rhodesian trypanosome, in 
the possession of a posterior nucleus, has not been recorded before. 
As to the meaning to be attached to these forms, we will consider the 
following main possibilities :-— 
(a) That we are dealing with a “variety” or “local race” of Z. gambiense 
due to some change of environment. The possibility in this case exists of 
T. gambiense having been conveyed by a species of Glossina other than 
Glossina palpalis, which may account for the peculiar morphology we record ; 
but it must be added that we have no knowledge of any other trypanosome 
undergoing similar changes owing to sucha cause. That it is a “ laboratory ” 
variation we think is out of the question, as all the known laboratory strains 
of 7. gambiense are practically identical in morphology. | 
(>) That we are dealing with a new species of trypanosome also producing 
Sleeping Sickness in man. In support of this view there is firstly, the 
morphology, which considered alone is strong evidence, since the Rhodesian 
trypanosome differs from 7. gambiense more than, for instance, 7. brucei does 
from 7. evansi. Secondly, there is the history, taken in connection with 
the fact that, so far as we know, 7’. gambiense is conveyed solely by Glossena 
palpalis, but even should it prove that Glossina palpalis exists in the 
districts through which W. A. travelled, then all the more probable is it 
that we are dealing with a new species of trypanosome. 
It seems to us, however, that it is difficult in the absence of further 
knowledge to discriminate with certainty between these views. Yet, on 
account of its peculiar morphological features, this Rhodesian trypanosome 
at least merits a distinct designation as 7. gambiense rhodesiense, adopting 
the trinomial nomenclature. Our own view, however, is that we are dealing 
with a new species of human trypanosome for which we propose the name 
Trypanosoma rhodesiense. 
