A Trypanosome from Zanzibar. 



15 



Two rabbits were inoculated, one subcutaneously and one intraperitoneally. 

 The former was sent to Dr. Mesnil from Marseilles, but it has shown 

 nothing. It was twice inoculated with big doses, one from a horse and one 

 from an ox. The other Dr. Edington handed over to Dr. Bradford, and from 

 this rabbit the trypanosome under consideration was obtained and studied. 



On examining the rabbit's blood, the trypanosome was found to be a small 

 one, with poorly-developed undulating membrane, and no free flagellum. 

 The average length was only 13 - 5 microns. 



Although it is impossible in some cases to name the trypanosomes from 

 their shape and size alone, still it is evident that a trypanosome of this size, 

 with no free flagellum, cannot be Trypanosoma brucei, evansi, gambiense, or 

 several other species which need not be enumerated. The names of such 

 small trypanosomes as Trypanosoma nanum (Laveran), Trypanosoma congolense 

 (Broden), or Trypanosoma dimorphon (Dutton and Todd), at once occur to 

 the mind. 



No doubt the tendency in naming these heematozoa is to multiply 

 unnecessarily the number of species. But, on the other hand, it is just as 

 great a mistake to lump too many species together, as has been done. If 

 there is some well-marked difference in two trypanosomes, even if alike in 

 shape, such as their power of setting up disease in certain animals, their 

 mode of spreading from the sick to the healthy — it may be in one by tsetse 

 flies, in another by stomoxys, or tabanus, or by other means — then, naturally, 

 it is of great practical use to distinguish them by different specific names. 



Again, it might be argued, that if two trypanosomes were different 

 morphologically, but had the same effect on animals, the same distribution 

 and the same carrier, then the two varieties for practical purposes might be 

 included in the same species. 



For example, when we have to do with Trypanosoma gambiense we at once 

 know that man is susceptible, that the carrier is Glossina palpalis, and that 

 we must keep ourselves out of the area of distribution of this fly if we 

 would escape infection. Theories in regard to the spread of sleeping 

 sickness by mosquitoes, stomoxys, fleas, sexual intercourse, and such like, 

 may, for practical purposes, be ignored. If it is Trypanosoma brvxei, then 

 we know man is not susceptible, but that we must keep our horses, cattle, 

 and dogs out of the area of distribution of Glossina morsitans. 



The three most important questions to be borne in mind, in classifying 

 trypanosomes, are, what animals are they capable of infecting, the gravity of 

 the infection, and, thirdly, what is the carrier ? To these may be added 

 the morphology of the trypanosome, its cultural characteristics, if any, and, 

 if possible, cross-inoculation experiments. If these several facts could be 



