456 
Trypanosoma gambiense 
methods of fixation. A thousand trypanosomes in the middle area of 
tlie film were then carefully drawn, with the aid of a camera lucida, 
to a magnification of 3000 diameters (Zeiss 2 mm. ap., oc. 18), care being 
taken to avoid missing any of the parasites or going over any part of 
the slide more than once. When the requisite number of drawings 
had been made, the length and breadth of each were carefully measured 
and the dimensions arranged in the form of a table. The length was 
taken along the axis of the body, from the posterior extremity to the 
extreme tip of the flagellum, and in order to obtain this measurement 
a “ map measurer ” was employed, with the aid of which it is easy to 
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60 
40 
30 
20 
10 
0 13-3/j 20/z IG-Qf! 33-3/i 40// 46-6// 
Curve A. Illustrating the relative frequency of trypanosomes of equal length. The 
length of the parasites is measured along the horizontal line and the number of 
individuals along the vertical, each dot corresponding to one trypanosome. 
