1912.] On the Extrusion of Granules by Trypanosomes. 381 



movement and appear to throw themselves against the periplast and rebound 

 from it. Sometimes the granules approach the surface, and in so doing 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 decree 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, but 

 from some point near the middle of the trypanosome body. 



In infections running a very rapid course — such as T. bmcei and 

 T. rhodesiense in white rats — -extrusion is readily observed, whereas in sleeping 

 sickness in man, a very chronic infection, prolonged search may be necessary. 

 Certain intermediate types of the disease are particularly suitable for study 

 of this subject — for instance, T. brucei in gerbils, as described above. In the 

 course of this infection granules are not extruded when the trypanosomes 

 first appear. At a later stage the phenomenon is easily seen, and again it 

 cannot be observed just before disappearance of trypanosomes from the 

 blood. These facts tend to confirm our opinion that extrusion occurs at 

 a definite period in the life of an adult trypanosome. 



Extrusion can be stimulated by the administration of drugs and by certain 

 mechanical effects such as variations in osmotic conditions. Eeference is 

 made to extrusion induced by varying strengths of salt solution in a later 

 .section of this paper. 



Under ordinary circumstances extrusion of granules does not appear to 

 have a prejudicial effect on the trypanosome. In warm wet preparations it 

 can be seen to continue its movements and it apparently lives as long as the 

 others. On the other hand, it has been shown above that 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 unfavourable circumstances, e.g. after treatment, extrusion is 

 followed by rapid disintegration of the trypanosomes. 



III. Effect of Drug Treatment on Extrusion. 



Certain phenomena in connection with the liberation of granules have 

 been observed after treatment with antimony. Cases of sleeping sickness 

 were given an intravenous injection of metallic antimony, and gland-puncture 

 wet preparations made at short intervals after treatment, 3 minutes, 5 minutes, 

 and so on. These were examined by dark -ground illumination and the results 

 of the observations are here described. 



Extrusion of granules is more frequent. The exaggerated motility is one 

 factor, and the protoplasm, and more particularly the periplast, seem to lose 

 elasticity, with the result that the granules can get free more easily. If a 



