16 



Neurorydes hydrophobiw — {Negri bodies). Diagnosis of rabies a 

 slow process until Negri's discovery, in 1903, of peculiar bodies 

 found in nerve cells of animals affected. Most numerous in cells of 

 hippocampus major. Size up to 25/j. Believed by good authorities 

 to be protozoon in nature because evidence of typical nucleus, growth, 

 reproduction by simple division and budding. Sarcodina.'' 



Sub-Phylum MASTIGOPHORA 



Tr3rpanosoma brucei — The cause of the tsetse-fly disease or 

 "nagana" of domestic animals in South Africa. Duration of diseases 

 few days or weeks to many months but always fatal in horse and 

 donkey, very few cattle recover. Supposed to be due to bite of 

 tsetse-fly. Parasite discovered by Bruce, 1874, free in blood plasma. 

 See Bruce, '07, and Laveran and Mesnil. 



Structure — Spindle-shaped body, with a more or less spiral 

 twist and with one edge provided with delicate, undulating membrane. 

 Flagellum arising near posterior end at a highly refractile granule 

 known as the "blepheroplast" and continuing as the thickened edge 

 of the undulating membrane, to project at anterior end. A micro- 

 and a macro-nucleus present. 



Movements — Exceedingly rapid. When parasites are abundant, 

 they may be detected under moderate power by motion of blood 

 corpuscles. Usually present in small numbers and blood must be 

 centrifuged to find them. Euglenoid movement. 



Reproduction — Longitudinal division. Sexual reproduction in 

 dispute. 



Artificial culture — One of the few forms of protozoa which has 

 been artificially grown with marked success. First grown by McNeal 

 and Novy, '03, on nutrient agar and defibrinated rabbit's blood. 

 Influence of this work on study of parasitic protozoans important. 



Method of transferral — Solely by tsetse-fly, as shown by Bruce's 

 experiments, 1894. Infective for 48 hours after feeding on sick 

 animals. Evidence that there is then a latent period after which the 

 flies again become infective. 



Prophylaxis — Protection of cattle from bites of the fly. Destruc- 

 tion of big game. 



Related species — Group a large one, over sixty species being known, 

 some apparently harmless but among them some of the most danger- 

 ous parasites. 



