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162 other, which is a sharply defined refractile body, being concerned in the process they describe. Their description refers to T. gambiense,but they have witnessed a similar process in other species of trypanosomes.

Referring to T. gambiense, they write:—— " In this species the granules are multiple and move rapidly backwards and forwards in the long axis of the trypanosome. They exhibit also a dancing movement and appear to throw themselves against the periplast and rebound from it. Sometimes the .granules approach the surface, and in doing so may actually cause a slight protrusion on the covering membrane. This seems to be preliminary to extrusion, as afterwards the granule may be shot out with a certain degree of force into the free fluid to some distance from the host. In this species extrusion is not as a rule effected from the extremity (as in T. nanum) but from some point near the middle of the trypanosome body. " Extrusion of granules, if occurring generally, apparently heralds a disappearance of trypanosomes from the blood and is, in fact, the precursor of a trypanolytic crisis. Under favourable circumstances, e.g. after treatment, extrusion is followed by rapid disintegration of the trypanosomes." As regards the granules, they state that there is "a definite sequence of events during an exacerbation of the disease: (1) Trypanosomes without granules; (2) trypanosomes showing granules which gradually become larger and very evident; (3) many free granules; (4) many trypanosomes but no granules; (5) trypanolytic crisis, or death of the animal. "

After extrusion the granules, which are now motile, if they escape the phagocytes, undergo the developmental change illustrated in Fig. 46. Rôle of the tse-tse fly.—— An important practical point is the question of the transmission of the parasite. As already mentioned, the well- and long-known role of the tse-tse fly* in the transmission of the trypanosome of nagana suggests that the corresponding parasite of man is transmitted by a corresponding insect, a suggestion borne out by considerations of distribution, and by experiment. Minchin, Gray, and Tulloch have shown that when Glossina palpalis was half fed on a rat infected with the cattle trypanosome of Uganda (probably T. brucei), and immediately transferred to complete its meal on a healthy rat, in four out of five