ARGUMENT 
It must be admitted that our present knowledge of trypanosomes 
does not permit of any satisfactory classification. In Africa the 
confusion in nomenclature is appalling, and the number of specific 
or suggested names, based largely upon the country of origin or the 
first found host rather than upon morphological or biological 
characteristics, renders absolute diagnosis of an individual form 
almost impossible without a typical living strain for comparison. 
There is perhaps no great difficulty in asserting that the body 
structure of certain trypanosomes sliows dimorphic variations under 
certain conditions. In all trypanosomes morphological differences 
between individuals occur to a greater or lesser extent, but only in the 
one species, T. dimorphon, Dutton and Fodd, are they considerable. 
In this, unless the ‘ tadpole ’ and the ' long ’ be seen, they are not 
striking; and between the larger of the ' stumpy' and the shorter of 
the ‘ long' we do not consider the variations greater than between 
some of the so-caTled ‘ male ‘ and ‘ female,' or the smaller or the larger 
forms of T. evansi. An additional difficulty is that there is no one 
structural point that can be seized upon as a basis for classification; 
most gradations can be met with in the shape of the posterior 
extremity and the length of the anterior and the amount of the 
flagellum that is free. As we have found forms recognisable as 
‘ tadpoles ' and ‘ long ’ both under natural conditions and those of 
ordinary animal experimentation, we have no hesitation in asserting 
that the cattle trypanosome first described is dimorphic according to 
the interpretation placed upon that word by workers on trypano¬ 
somiasis. 
The first dimorphic trypanosome was that described in the Gambia 
by Dutton and Todd,* who at the same time described the patho¬ 
logical reactions produced by it there, which reactions were later 
confirmed in Europe by Thomas and Breinl,^ and by Laveran and 
Mesnil.^ They showed that rats, guinea-pigs and, with one 
exception, dogs are susceptible, and die within one or two months. 
The trypanosome encountered in the cattle of the Congo Free State 
was also dimorphic in type, but the animal reactions in that country 
differ from those obtained in the Gambia. At one post, Roinee. 
laboratory animals were shown to be highly susceptible; at the other 
