36 ALLEGED IMMUNITY OF DONKEY. 



hinted at less than ten years after the date of Erskine's paper.* 

 St. Vincent Erskine's theory, although attacked shortly after- 

 wards by E. C. Buxton [41], was warmly espoused by the well- 

 known English entomologist, Edward Newman [39, 44], who 

 considered the Tsetse to be a " myth." 



A second letter from Karl Mauch [40], published in 1870, 

 contained an early expression of the commonly accepted idea 

 that the donkey is immune to Tsetse-fly disease. Writing of the 

 behaviour of a donkey in the Fly country in the Northern 

 Transvaal, Mauch says : — ■" The main advantage, however, con- 

 sisted in the fact that the Tsetse could not do her any harm, 

 whether it be that the donkey finds in certain leaves or in the 

 bark of certain trees an antidote against the poison, or that the 

 long hair or the efiluvium from the beast repels the insect." f In 

 this letter Mauch also recorded the uselessness of sal ammoniac, 

 administered internally, as an antidote to Tsetse-fly disease in 

 cattle. A map by A. Petermann to illustrate Mauch's travels, 

 published in the same volume as the letter, shows the " Limit of 

 the Tsetse-fly " in the vicinity of the Limpopo, and also to the 

 south of the Zambesi. 



Eduard Mohr [42] met with the Tsetse in 1870 to the south 

 of the Victoria Falls, but Otto Kersten [43], who took part in 

 Baron C. C. von der Decken's travels in East Africa from 

 1859 to 1865, did not encounter it between the coast and 

 Dschagga (the region of Mt. Kilima Njaro), though later on he 

 mentions its occurrence on the Lower Juba River as the reason 

 why the Wabuni, a scattered tribe of Galla, are unable to keep 

 cattle.J Stanley [45], in " How I Found Livingstone," published 

 in 1872, recorded his experience with Tsetse-flies, and mentioned 

 native names under which they are known in different regions. 



* Livingstone himself [21] appears to have partially realised the truth. 

 After describing the effects of the bite of the Tsetse-fly in cattle, he 

 proceeds to say (" Missionary Travels," p. 82) : — " These symptoms seem 

 to indicate what is probably the case, a poison in the blood ; the germ of 

 which enters when the proboscis is inserted to draw blood. The poison- 

 germ, contained in a bulb at the root of the proboscis, seems capable, 

 although very minute in quantity, of reproducing itself, . . ." It is 

 evident, however, that Livingstone supposed the fly to possess a poison- 

 gland, situated in the bulb at the base of the proboscis, the secretion of 

 which was fatal to cattle. 



t Col. Bruce's experiments showed that Tsetse-fly disease is invariably 

 fatal to the donkey in Zululand (see Chapter Vll., Appendix A). 



X Probably this is the earliest definite reference to the Somaliland 

 Tsetse-liy, described long afterwards by Corti as Glossina longipennis : 

 if so it is interesting as evidence that a species of Glossina distinct from 

 Gl. morsitans is able to carry the hsematozoon. (C/. Chapter VII., 

 Appendix E.) 



