TRYPANOSOMIASIS EXPEDITION TO SENEGAMBIA 
37 
Its protoplasm stains deeply. Its posterior end is either sharply cut away or bluntly 
conical. The body tapers from the posterior end as a rule, and is prolonged anteriorly 
into a short fine flagellum. 
The micronucleus and vacuole are placed almost at the extreme posterior end 
ot the parasite, the former is a small dark crimson staining spot generally situated to 
one side, the latter varies much in size in different specimens. The macronucleus is 
generally rounded, granular, and does not quite extend across the short axis ot the 
body. The blue staining body-protoplasm of some specimens contains a few isolated 
chromatic granules. The undulating membrane is narrow and is seen with difficulty 
in stained preparations. 
The measurement ot this type of parasite in stained preparations is as 
follows : — 
Length, including flagellum, II fx to 13/* . Width, o - 8 fx to 1 /x. Distance 
from micronucleus to centre of macronucleus, 4 fx to 6 /x. Distance from micronucleus 
to posterior end of body, 0*3 fx to o - 5 m. Divisional forms ot this small parasite are 
represented in Plate I, fig. 8. 
In horses in the last stage ot the disease and in rats inoculated with either 
the human or horse trypanosome, we were generally able to distinguish roughly two 
constant types ot parasite. These types we called tor convenience the ' long form ' 
and the ' stumpy form ' ot the parasite. 
A. — The long form (Plate I, figs. 9 and 10) is characterised by a long thin 
body and a long flagellum. The posterior end of the parasite may be long (pointed 
or square shaped) or stumpy and conical. The deeply staining macronucleus is ovoid 
in shape and lies longitudinally. It is this type of parasite that multiplies by longi- 
tudinal division. The length ot such a parasite, including the flagellum, is from 
26 fx to 30 fx ; width, i"6 m to 2 m. Distance from micronucleus to centre ot macro- 
nucleus, 7 m to 8 m. Distance from micronucleus to posterior end ot body, 1*6 m to 
3 '2 fx. 
This type can be recognized in fresh blood by its rapid movements and long 
flagellum, and is usually most numerous in the blood ot an intected animal a tew days 
before its death. 
B. — The Stumpy form (Plate I, Fig. 7). 
This type ot parasite is more commonly seen in the blood when the disease 
in an intected animal is not tar advanced. It is characterized by a short thick body 
and very short flagellum. The posterior end is short and conical, and generally quite 
close to the tip is situated the micronucleus and vacuole, the latter as a rule is well 
marked. 
The macronucleus is either oval or circular in shape. It it is ovoid it is placed 
transversely in the body of the parasite. A few scattered chromatic granules may be 
seen in some specimens. 
