THE GENUS TRYPANOSOMA 261 



eijd — and, seen alone, such a stage might be wrongly interpreted as 

 transverse division (Fig. 102). Very often the cells divide without 

 becoming entirely separated, repeated divisions following one another 

 until rosettes are formed. A very remarkable process of multiple 

 division was described by Button, Todd, and Tobey ('07) in Tryp. 

 loricatum, a parasite of African toads and frogs; here the organism, 

 by repeated binary division, gave rise to more than forty cells, "all 

 apparently inside the outer covering of the original trypanosome" 

 (op. cit., p. 312). Such a process of multiplication is cjuite novel for 

 trypanosomes, and needs confirmation. 



E. Agglomeration. — Rosettes due to incomplete division are 

 quite different from the aggregations of trypanosomes known as 

 agglomerations, which are due to abnormal conditions of the environ- 

 ment, or, as Laveran and Mesnil first observed, may be phenomena 

 due to decreasing vitality. It may be brought about in the blood by 

 mixing immune serum with the normal infected blood, by addition of 

 weak chemicals (e. g., acetic acid), by lowering the temperature, or by 

 conditions arising in artificial culture media, Novy and MacNeal 

 finding agglomerations of more than a thousand cells at times. 



F. The Invertebrate Hosts and Life Cycle of Trypanosomes. — 

 At the present time nothing can be farther from settled than the 

 happenings within the bodies of invertebrate hosts of trypanosomes, 

 and much unfortunate controversy of an entirely unnecessary char- 

 acter has been filling the pages of medical and scientific journals. 



Although mammalian tr^'panosomes were first observed and 

 described by Lewis, in 1S77, for Tryp. leivisi of the rat and in 1880 for 

 Tryp. evaiisi, the cause of surra in horses, little importance was 

 attached to them as the causes of disease until Bruce,, in 1894, demon- 

 strated the connection between the disease nagana of horses in Africa 

 of unknown etiology, and the tsetse fly diseases of horses. The history 

 of this discovery is best given in his own modest account, while at the 

 same time it reveals the modus operandi in establishing the connection 

 between invertebrate host and protozoan parasite. "In October, 

 1894," says Bruce, "when serving in Natal, South Africa, the governor 

 of that colony, the Hon. Sir Walter Hely-Hutchinson, G.C.M.G., 

 asked me to go to Zululand to report on a disease which was causing a 

 severe loss among the native cattle. The native name of the disease 

 was nagana. At this time no suspicion that nagana and the tsetse fly 

 disease were identical was entertained. The writer at once proceeded 

 to Zululand, and after a month's travelling by ox wagon from Eshowe, 

 the capital of the country, arrived in the infected area. A small 

 laboratory having been set up and some of the affected cattle obtained 

 from the surrounding natives, examination by the ordinary bacterio- 

 logical methods was begun. The animals were emaciated, with staring 

 hair, some fever, and sometimes edema of the subcutaneous tissues of 



