136 TRYPANOSOMIASES OF RHODESIA. 



the recent extension of this plague in Rhodesia cannot be over- 

 estimated. [Moreover, the danger which menaces us is beset with 

 more than usual difficulties by reason of the uncertainty which 

 exists as to the identity of the species of trypanosome and the 

 manner in which the disease, which is of exceptional virulence, 

 is spread. For while human trypanosomiasis in the past has been 

 intimiately associated with the Glossina palpalis, recent cases 

 seem to have been contracted where this fly is not known to 

 exist. Until these uncertainties are cleared up adequate methods 

 of prophylaxis cannot be devised, and the possible limits of the 

 danger not only in this country but in the sub-continent cannot 

 be defined. 



The trypanosomes are Protozoa of the class FJagcUata, 

 whose usual form is spindle-shape or fusiform, varying in dif- 

 ferent species and in many circumstances. The body consists of 

 a thin outer periplast surrounding an inner granular endoplasm. 

 About the centre of the endoplasm is a trophonucleus, believed 

 to be largely concerned in nutrition, while situated generally 

 near one extremity is another mass of chromatin regarded by 

 some as a kineto-nucleus, by others as an extra-nuclear centro- 

 some. From this a faint strand proceeds which ends with a 

 little bead — the blepharoplast — from which arises a flagellum 

 running through the endoplasm to the ectoplasm, which it raises 

 into a fold, known fromi its festooning as the " undulating mem- 

 brane." The flagellum may project as a free lash beyond the 

 parasite, such portion being termed the free flagellum. Some 

 diversity of opinion exists as to which end of the parasite must 

 be considered the anterior extremity, but in this paper the non- 

 flagellated end will be regarded as the posterior. The endoplasm 

 often appears vacuolated, and chromatoid granules are scattered 

 in it in varying size and numbers. Some authorities describe 

 longitudinal striations which traverse the body and aft'ord a cer- 

 tain contractility to the organism, and produce variations in shape. 



The trypanosomes are capable of movement, the undulating 

 membrane, free flagellum and contractility of the body taking 

 part in locomotion. The degree and manner of movement is 

 often characteristic of a species ; thus the Tr. vivax of animals 

 encountered in Northern Rhodesia is so called on account of 

 the rapidity and violence of its passage through the microscopic 

 field. 



The greatest importance has been attached to the morpholog>' 

 of the trvpanosomes, and elaborate systems of measuring and 

 diiTerentiating have been devised, with the result that innumer- 

 able species have been identified. The smallest irregularity in 

 any specimen has prompted some extremist to create a new 

 species, with the result that at the present day the classification 

 of African trypanosomes is in a state of chaos. The chief points 

 .seized upon for this purpose have been : — 



(a) Measurements, such as the length and width of the 

 various portions of the parasite and the total length of the 

 whole. 



