PROTOZOA 383 



THE FLAGELLATA. 



General description. The flagellates are motile protozoa. 

 Their organs of locomotion are flagella or whip-like processes 

 which arise as a rule from the anterior part of the organism. 

 In motion the larger ones (primary flagella) are directed for- 

 ward while the smaller ones (secondary ones) are directed 

 backward. 



There is a great variety of these forms. As a rule, their 

 structure is more fixed in outline than ameba. It is stated 

 that this is due to the fact that they usually have a somewhat 

 definite but delicate membrane containing elastic fibers. They 

 reproduce either in the free motile state or after they are en- 

 cysted. In the first case as a general thing they divide longi- 

 tudinally. The basal ganglia and flagella divide with the 

 nuclei. Multiple division is also observed. In the second case, 

 they may or may not conjugate before they encyst. Division 

 forms occur in the cyst by a process similar to that in the 

 amebae. It has been stated by Schaudinn that certain of these 

 forms pathogenic for man require a second host for the de- 

 velopment of their sexual cycle. 



The orders of flagellates which possess species pathogenic 

 for domesticated animals are the Monadida, which contain the 

 genera Piroplasma, Trypanosoma and the Spirochaete. 



GENUS PIBOPLASMA (fiABESIA) SMITH AND KILBORNE. 



In 1888, Babes * described bodies in the red blood cells in 

 Roumanian cattle affected with a somewhat fatal disease that 

 up to that time had not been understood, but which was sim- 

 ilar to that known in the United States as Texas fever. He 

 described these bodies somewhat indefinitely. His inference 

 seemed to be that they were micrococci. In 1893, Smith and 

 Kilborne 2 described the organism of Texas fever, and named 



1 Babes. Compt. rendu de 1'Acad. de Sci., Vol. CVII (1888) p. 

 692. 



2 Smith and Kilborne. Texas fever Bulletin No. 1, B. A. I., 

 U. S. Dept. of Agric., 1893. 



