ANIMAL TKYl'ANOSOMIASES IN THE ANGLO-EGYl'TIAN SUDAN 43 



Tijpe 2. T. evansi, affecting camels from Kordofan and Erkowit. In classing some of 

 our known strains under this heading we are on less debatable ground than is certainly 

 the case with two of the other types. Its general host here is most undoubtedly the camel, 

 it is rarely dimorphic, and its morphology, as will be shown in detail, approximates to 

 the evansi type ; moreover, its animal reactions resemble those of the Indian Surra. 



Type 3. T. nanum or pecorum. This form has been found by Balfour to occur in 

 epidemic form in the Shilluk cattle, and Drew came upon a similar type in goats near Eagaa 

 in the Bahr-El-Ghazal. A specimen from the first of these sources was named T. nanum 

 by Laverau, from films sent him by Balfour, in 1905. Wenyon, in the Third Eeport, speaks a possible 

 of T. nanmii as occurring among mules and donkevs in the Bahr-El-Ghazal, and describes error in 



• -1 ■ *T p Tpi- -ii classification 



under this heading two main types with an intermediate form. A study of his article has 

 led us to the conclusion that he was dealing with some other kind of trypanosome, because, 

 for one thing, uniformity of morphology is considered by us to be an outstanding 

 characteristic of this species. The reason that T. pecorum has been included in the 

 nomenclature of this type is the strong morphological similarity between some specimens 

 obtained from the cattle and goat infections, and the T. pecorum described by Bruce 

 and others in the communication to the Royal Society, of June, 1910. 



Tt/pe 4. T. vivax or cazalboui, from cattle in Kassala Province. This trypanosome, 

 considerably shorter than T. evansi, is so typical on account of its extraordinary motility 

 and its animal reactions, that, for this type, differentiation is simple. The question of the 

 distinction, if any, between T. vivax and cazalboui will not be entered into here. 



We shall now briefly discuss in general the means which are at present at our Methods of 



, . . , , , iTip differentiation 



disposal for differentiating trypanosomes, and it is here urged that some settled plan of 

 procedure on the part of all observers would go far to prevent the inundation of scientific 

 literature with the profitless discussions which arise round the nomenclature of similar 

 type trypanosomes occurring in various parts of the globe. We have, at present, five 

 possible headings, of varying importance and usefulness, under which classification may 

 be attempted. 



These are : — 



1 , . . ... ... ... Morphology 



'2 ... ... ... ... Auimal inomilations and reactions 



3 ... ... ... ... Culture 



•i ... . . ... ... The question of the carrier 



5 ... ... ... . . Reaction to drugs 



These headings w-ill now be gone into, a few words also being said about what is 

 known as cross-iiioculatiou, and it will be seen that by an application of some or all 

 of these means a trypanosome can be classified with a reasonable amount of certainty, 

 but it must at the outset be made plain that a certain degree of simplicity and definiteness 

 is essential for satisfying the clauses under these headings, for as surely as the methods 

 of identification are made numerous and complicated, so surely will the risk of unnecessary 

 division of types increase. Not only are the relative values of the above headings of 

 themselves far from being equal, but they also vary in value as a means of distinction 

 for the different trypanosomes. 



In the first place we have morphology, and this, under some circumstances, is Morphology 

 absolutely straightforward ; for instance, no one seeing a slide of T. nanum, from general 

 morphological considerations, would confuse it with T. evansi ; but in most cases, and for 

 trypanosomes of a somewhat similar structure, something more definite is required, and 



