RELATION.OF ARTHROPODS TO PATHOLOGY—-MAROTEL. 709 
1901 by the American commission in Cuba have shown that it is 
exclusively due to the bite of a mosquito, Stegomyta calopus. In 
fact, by forty different repetitions this commission was able to re- 
produce yellow fever experimentally by causing healthy individuals 
to be bitten by infected Stegomyia. In addition these results, which 
constitute a striking confirmation of the mosquito theory, already 
advanced twenty years earlier by Finlay, were verified almost im- 
mediately in different places at the same time. In 1902 by Guiteras 
in Havana, in 1903 by Ribas and Lutz at St. Paul, as well as by a 
second American commission which worked at Veracruz; finally, 
in 1904, by a French commission sent to Rio de Janeiro. As a result 
the transmission of yellow fever by mosquitoes is no more doubted 
to-day than that of malaria and certain forms of filariasis. 
D. TRYPANOSOMIASIS. 
Trypanosomiasis, as one may guess, is a disease caused by the try- 
panosomes, that is to say, by miscroscopic infusorians with a fusi- 
form, sinuous, or arched’ body, possessed of an 
undulating lateral membrane and a terminal fila- 
ment, called a flagellum (fig. 5). 
These parasites live also in the blood of their 
host, but with the difference, as compared with 
Plasmodium (which are lodged within the cor- 
puscles), that they swim in the plasma. They 
therefore are exoglobular hematozoans. 
At present, nine species of trypanosomes are 
known which are capable of attacking man and 
domestic animals. They cause, on almost the pe 5, trypanosoma 
whole surface of the globe, the epidemics, the brucei of Nagana x 
: : - 2,000. After Laveran 
cause of which long remained a mystery, and of fa Mesnil. n, Neu- 
which the prophylaxis is one of the major prob- cleus; ¢, centrosome ; 
lems of colonial expansion. pnegelinny: 
The most dangerous forms are: 7rypanosoma brucei, the agent of 
an African trypanosomiasis, the “nagana,” which attacks chiefly 
cattle; Trypanosoma evansi, which causes “surra” among horses 
and Asiatic cattle; 7rypanosoma equinum, the agent of “ caderas” 
among American horses; 7rypanosoma equiperdum, agent of “ dou- 
rine;” Trypanosoma gambiense, which causes in man an affection of 
which the two periods, the initial and the final, were quite recently 
still described as two absolutely distinct diseases, having nothing in 
common between them. The initial period was called Gambia fever, 
while the final stage was the famous “sleeping sickness,” well known 
to the African colonists. 
In addition to these principal species, there are others, less impor- 
tant, and also less studied, such as 7rypanosoma theilert, which causes 
