424 VETERINARY BACTERIOLOGY 



scribed another form from Africa as the cause of nagana or tsetse- 

 fly disease. Since that time the number of known species has in- 

 creased rapidly. A small proportion only of those described are 

 known to be pathogenic. Among the pathogenic forms, however, 

 are to be found those that are among the most serious hindrances 

 to the development of a live-stock industry, and even to human 

 habitation in certain countries. 



Morphology. Trypanosomes usually are elongated cells, more 

 or less spindle-shaped, rarely almost as broad as long, but always 

 tapering more or less to the ends. Most of the pathogenic forms 

 that have been described are several times as long as broad when 

 observed in the blood. The anterior end of the cell is tipped with a 



Fig. 188. Trypanosoma equiperdum, morphology of the try panosome : 1, 

 A rather thick, short trypanosome a, Blepharoplast ; b, protoplasm (cyto- 

 plasm); c, nucleus; d, undulating membrane; e, flagellum attached to the edge 

 of the membrane; /, anterior extension of the flagellum. 2, A longer cell. 

 3, 4, Trypanosomes in process of longitudinal division (adapted from Gonder 

 and Sieber). 



flagellum. Along one side, extending longitudinally on the cell, 

 is a thin membrane. The flagellum extends along this membrane 

 and forms its outer edge. The flagellum finally terminates in 

 the cell-protoplasm near a granule which stains deeply. This 

 granule may be situated in various parts of the cell, but is usually 

 in the posterior portion. Its relative position is one of the charac- 

 ters used in the differentiation of species. It has been called by 

 various names, as micronucleus, kinetonucleus, motor nucleus, 

 centrosome, and blepharoplast. This last name is to be preferred, 

 as it is the one that is most frequently used in the descriptions, and 

 is commonly used for similar structures found in many other 

 flagellated protozoa. The flagellum is, in part, therefore, em- 



