TRYPANOSOMIASIS EXPEDITION TO SENEGAMBIA 57 
Fourteen of the former in all were examined, and in the blood of three, 
flagellated protozoa were seen. Twenty field mice were examined, but none were 
found to be infected. The organism occurred infrequently in the blood of the mice 
infected, and we never saw more than one or two parasites in a fresh coverslip 
preparation. 
The organism was striking, in that it presented characteristics which 
differentiated it, at a glance, from a trypanosome. It consisted of a long oval-shaped 
body with blunt rounded ends, to one of which a very long flagellum was attached. 
At this end the body tapered slightly. A glance showed that the long flagellum, 
slightly longer than the body, was the chief organ of locomotion. It acted as a 
tractellum, and obviously dragged the body of the parasite after it. On encountering 
an obstruction the flagellum lashed out in all directions, hurled the red cells 
behind it, and often twisted round, so that its tip reached past the posterior end of 
the body. On these occasions, it was easy to examine the structure and measure the 
length of the parasite, as the body was perfectly quiescent. The protoplasm has a 
slightly granular appearance and in its substance, placed a little in front of the centre 
and towards the flagellated end, is a collection of refractile granules. About 5 /u. 
from the anterior end is seen a highly refractile spot from which the flagellum takes 
origin. No suggestion of an undulatory membrane was seen. The length of the 
body in the living condition is 2cr8 m, and its greatest width 3-2 fx. The body of 
the parasite sometimes assumed an 'S'-shaped form, on account of external pressure 
or rapid changes of direction of movement, but no active contractions of the proto- 
plasm were seen. 
Unfortunately, two mice sent home infected with this parasite died on the 
voyage, and in the films made from the mice while in Gambia, no specimens have 
been seen. A small rat inoculated from one of the mice has not shown the parasite 
in its blood. No symptoms were observed in the mice infected. 
This parasite resembles very closely Herpetomonas {Leptomonas) ButscJili (S. 
Kent). The figures given of this organism correspond very closely with our flagellate, 
except that in the mouse parasite there is not the marked tapering of the non- 
flagellated end of the body. Herpetomonas Butschli, however, inhabits the intestinal 
tract of Trihbus Gracilis, and not a vertebrate circulatory system. 
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