ANTMAI. Tr.VPAXOSOMIASKS I\ THE AXOT,0-EOYrT[AN SUDAN 45 



Tliis will readily he understood if ability to produce antimony-fast and arsenic-fast strains 

 be acknowledged, and the great want of uniformity of result between the action of a similar 

 dose of a drug on similar animals, which have been infected at the same time, be known. 

 Finally, as to Laveran's cruss-jnoctdafimi method, which depends on the fact that doss- 

 animals naturally recovered from a trypanosomiasis cannot again be infected with the 

 same disease though still susceptible to other strains, its application is necessarily limited ; 

 for unless a large number of " immunes " be kept up, a considerable time is required to 

 prepare an immune animal. This difficulty is increased bj- the fact that animals in which 

 trypanosomiasis is an acute disease die when inoculated, while those in which it is 

 chronic, live on, presenting us with the difficult problem of accurately fixing the time 

 of recovery. Also, unless the experimental animal is to some extent resistant to the 

 trypanosome under investigation, it is lost to the laboratory. 



The method must be looked upon as cumbersome and not easy to carry out. 



In the writer's experience with T. evan$i, animals cured by drugs are as susceptible to 

 a secondary inoculation of the original trypanosome as they were to the primary, a point 

 giving rise to more theoretical fallacies. On the whole, therefore, the method does not 

 appear suited to general tropical laboratory work. 



The introduction to this short study of the trypanosomes of the Anglo-Egyptian 

 Sudan was written with a view to make clear to the reader the general extent of our 

 present knowledge on the subject, and also to convey, in general, an impression of the 

 main principles which have been observed in making this study. 



If the second object has been attained, the importance attached to the vai'ious 

 phenomena recorded in connection with our four types will be readily undeistood, 

 certainly at least as far as the work of classification goes. 



A confession of faith on the part of a writer of a scientific article would go far 

 sometimes to rendering his writings intelligible. An ignorance of the axioms and postulates 

 governing his observations renders them often needlessly obscure. 



The general acceptation of Koch's postulates must have prevented endless discussions 

 on the pathogenic bacteria, for they make clear an observer's view-point. 



As no such general postulates are forthcoming on the subject of protozoal infections, 

 it is pleaded that there is justification for indicating a point of view before entering 

 into the treatment of a subject like trypanosomiasis, of which the manifestations are as 

 varied as the manifestations of grace. 



The four types have been described roughly in the order of what is at present 

 considered to be their relative economical importance ; and the amount of work done 

 on them follows closely in the same sequence. 



Type 1 

 7'. hnicei or ppcaiidi (Plate I., figs. 1-2) 



The distribution of this trypanosome is certainly of a very extensive nature and 

 probably affects numerous species of animals. Its occurrence as affecting more particularly 

 horses, mules and donkeys in the Bahr-El-Ghazal and on the White Nile, which has 

 already been mentioned, is far from leading one to suppose that it is limited to these 

 regions or to these animals. The outstanding characteristics of the type, as observed 

 here, are its well-marked and persistent dimorphic character and its virulence towards 

 dogs and the smaller animals. We have, as a point of interest, recently received 

 additional evidence that it occurs in the former as a natural infection. 



(a) Living and unstaiiu'd. An actively motile trypanosome occurring in two easily Morphology 

 recognisable forms, the long slender forms with a free flagellum and short stouter forms 



