22 
be noticed. Between the fourth and fifth hour the effect on the 
trypanosomes is evident. Some parasites appear to be swollen and 
their movement is less rapid. If now a series of blood specimens be 
examined at intervals of twenty to thirty minutes, the following 
changes will be seen. The number of slowly moving trypanosomes 
increases, many parasites will be seen to be almost motionless. The 
protoplasm takes on a peculiar ground-glass appearance, and dark 
granules appear in the protoplasm; very often a small series of 
granules one behind the other, sometimes in pairs or all clumped 
together, are seen lying between the macronucleus and the anterior 
end, or distributed through the whole body of the parasite. At the 
same time vacuoles are observed, oftentimes very large. The 
trypanosomes become deformed, assuming various shapes, the most 
common being a kite-shaped form with fairly long flagellum, and a 
tadpole-like one with hardly any free flagellum. These forms 
especially exhibit greatly impaired movements. At the same time 
a noticeable increase of the leucocytes is discernible; phagocytes 
begin to appear, very often groups of five to seven will be seen. 
Up to this time (sixth to seventh hours) the trypanosomes, though 
decreased in numbers are still present in considerable quantities. 
Suddenly, in the course of an hour, the numbers may drop from 
forty to two to three to a field or less; coincident with this is a 
very marked increase in the number of leucocytes, especially phago¬ 
cytes. From the ninth to the fourteenth and sixteenth hours the 
changes are less pronounced and rapid, the trypanosomes gradually 
disappear. At the eighteenth hour, provided the animal has been 
injected with the correct amount the parasites are absent from the 
peripheral circulation and. even though the blood is centrifuged 
none can be found. ^ ' 
From a senes of these observations, we have determined that in 
hardly any of the forty-six continuously observed animals were 
parasites to be found after the eighteenth. Should, however the 
drug be given in smaller amounts the process takes longer lalt ng 
from thirty-six to forty-eight hours. ^ lasting 
■From the experimental work with various therapeutic agents the 
following conclusions can be made agents the 
■(.) That animals suffering from trypanosome infection react 
