216 Arthropods as Essential Hosts of Pathogenic Protozoa 
While the disease is peculiarly African there are a number of 
instances of its accidental introduction into temperate regions. 
Slaves suffering from it were occasionally brought to America in 
the early part of the last century and cases have sometimes been 
imported into England. In none of the cases did the disease gain a 
foothold or spread at all to other individuals. 
In 1902 Dutton described a trypanosome, T. gamhiense, which he 
and Forde had found the year before in the blood of a patient suffer¬ 
ing from a peculair type of fever in Gambia. In 1902-1903 Castel- 
lani found the same parasite in the cerebro-spinal fluid of sleeping- 
sickness patients and definitely reported it as the causative organism 
of the disease. His work soon found abundant confirmation, and 
it was discovered that the sleeping sickness was but the ultimate 
phase of the fever discovered by Dutton and Forde. 
When Castellani made known his discovery- of the trypanosome 
of sleeping sickness, Brumpt, in France, and Sambon, in England, 
independently advanced the theory that the disease was transmitted 
by the tsetse-flv, Glossina palpalis. This theory was based upon the 
geographical distribution and epidemiology of the disease. Since 
then it has been abundantly verified by experimental evidence. 
Fortunately for the elucidation of problems relating to the methods 
of transfer of sleeping sickness, Trypanosoma gambiense is patho¬ 
genic for many species of animals. In monkeys it produces symptoms 
very similar to those caused in man. Bruce early showed that 
Glossina palpalis “fed on healthy monkeys eight, twelve, twenty-four 
and forty-eight hours after having fed on a native suffering from 
trypanosomiasis, invariably transmitted the disease. After three 
days the flies failed to transmit it.” In his summary in Osier’s 
Modem Medicine, he continues “But this is not the only proof that 
these flies can carry the infective agent. On the lake shore there 
was a large native population among whom we had found about 
one-third to be harboring trypanosomes in their blood. The tsetse- 
flies caught on this lake shore, brought to the laboratory in cages, 
and placed straightway on healthy monkeys, gave them the disease 
in every instance, and furnished a startling proof of the danger of 
loitering along the lake shore among those infected flies.” 
As in the case of nagana, Bruce and most of the earlier investi¬ 
gators supposed the transmission of the sleeping sickness trypano¬ 
some by Glossina palpalis to be purely mechanical. The work of 
Kleine (1909) clearly showed that for Trypanosoma gambiense as 
