SLEEPING SICKNESS. 33
ADDENDUM.
Since the main body of this paper was written a great deal
of work has been done both in the infected areas and in Eu-
ropean laboratories to clear up the questions concerning the
identity of the new Rhodesian trypanosome and its carrier.
Firstly, it has been shown that Trypanosoma Rhodesiense
(Stephens and Fantham) is not identical with Trypanosoma
Gambiense. This conclusion was arrived at by the considera-
tion of certain morphological differences; by the greater viru-
lence of the former trypanosome for laboratory animals than
the latter possesses and also by means of the "crossed
immunity test." The last named test showed that an animal
which was immune to T. Gambiense was still susceptible to
and died as the result of an inoculation with T. Rhodesiense.
Secondly, it was urged that T. Rhodesiense was in reality
the well known cattle trypanosome of South Africa (T. Brucei)
which is naturally carried by Glossina Morsitans and that this
parasite had recently become pathogenic to man. Laveran
from evidence obtained by his crossed immunity test and by
serum reactions came to the conclusion that the two were
distinct species. The evidence of morphology and of animal
reaction also goes to disprove the identity of these two try-
panosomes.
Thirdly, can G. Morsitans (the cattle tsetse fly) transmit
the Uganda form of Sleeping Sickness ? It has been proved
by many laboratory experiments that T. Gambiense can be
readily conveyed to monkeys and other animals by Glossina
Morsitans and that it was, therefore, possible that the fly
could take the place of G. Palpalis in areas unsuited to the
life of that insect.
At the same time opinions have been expressed that other
tsetse flies, Glossina Fusca and G. Brevipalpis may be found
to be capable of transmitting human trypanosomiases either
in Rhodesia or elsewhere. There is no evidence to show
that in nature the virus of Uganda Sleeping Sickness (T.
Gambiense) is carried by any tsetse fly except G. Palpalis