380 Major W. B. Fry and Captain H. S. Ranken. [Dec. 23, 



of blood examined granules have been found. Similarly in the case of 

 guinea-pigs and rabbits the blood has been found to be uniformly infective 

 during the so-called latent periods, when no trypanosomes can be found in 

 the blood by microscopic examination. 



II. Extrusion of Granule. 



The original observations have been repeatedly verified during the past 

 18 months, and we have been able to satisfy ourselves completely that 

 extrusion of granules is a constant feature of trypanosomal infections. 



The phenomenon has been observed in all species of trypanosomes studied 

 with the exception of T. leivisi. We were able to assure ourselves of the 

 presence of granules in that trypanosome, but the movements are so active 

 that definite extrusion was never witnessed by either of us. On account of 

 the high degree of motility the species was unsuitable for work on this 

 subject, and prolonged observations were not made. The mechanism of 

 extrusion has been studied in detail in T. nanum and T. gambiense. 



(1) T. nanum. — The strain was obtained from infected cattle from the 

 White Nile district, and, for the purpose of these observations, was kept up 

 by passage through gerbils. This type of trypanosome is very convenient foi- 

 the study of this process, as the granule is large and very evident and the 

 trypanosome, whilst evincing active lashing movements, does not progress 

 across the field of the microscope, but remains more or less stationary, so 

 that there is no difficulty in watching the same trypanosome through all the 

 phases over a period of several hours, if necessary. Further, an animal can 

 be selected at a period when extrusion is a frequent occurrence. 



When extrusion is about to take place the granule begins to work its way 

 slowly, but quite distinctly, from the centre of the trypanosome towards the 

 poirfted extremity. Arrived there, it makes its way back to the centre.. 

 This takes place quite often — as many as seven or eight such movements 

 having been observed. During these passages the granule can be seen 

 distinctly bulging the periplast as if becoming more and more superficial — 

 this bulging being strikingly apparent at the pointed extremity. Probably 

 this movement is largely due to the movements of the trypanosome itself.. 

 Finally, the granule, stretching the periplast to a greater extent, is extruded 

 suddenly from the pointed extremity and becomes a free element in the- 

 surrounding medium. Plate 9, fig. 1, illustrates all these stages. 



(2) T. gambiense. — Here the preparations were made direct from cases of 

 human trypanosomiasis. 



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. 



