PROTOZOA 



385 



infested territory and that the young ticks were able to trans- 

 mit the parasite to healthy or uninfected cattle. Further than 

 this the life history of this organism does not seem to be 

 known. As an etiological factor Piroplasma bigeminum de- 

 pends for its transmission upon the cattle tick. 



Morphology. As described by Smith, Piroplasma bigemi- 

 num appears in the red blood corpuscles of cattle suffering 

 from the acute form of the disease known as Texas fever as 



G) 

 Fig. 82. Piroplasma bigeminum in the red blood corpuscles. 



double pear-shaped forms and single rounded or more or less 

 irregular bodies; in size the average is from 2 to 4/x in length 

 and from 1.5 to 2.0 /* in width, the broad end tapering to a 

 point. In the double form the tapering ends come together. 

 In -the fresh blood the small forms are quite 

 homogeneous while the larger ones often ex- 

 hibit in the broad end a somewhat rounded 

 body from 1 to 2 /x in diameter which is 

 glistening and stains darker than the rest of 

 the organism. Ameboid movements have been 

 observed in the central bcdy. 



Some differences occur in the description 

 of the organism by different writers. Smith 

 describes in the mild or chronic form of the 

 disease coccus-like bodies. These bodies seem 



to be those described by Theiler c as Ana- 



Fig. 83. Blood 

 in a capillary of 

 the heart show- 

 ing Piroplasma 

 bigeminum in 

 the red corpus- 

 cles. (After 

 Smith and Kil- 

 borne. ) 



plasma marginale. In films made from the 

 blood of acute cases of Texas fever dried in 

 the air and fixed either by heat or by a fixa- 

 tive, the organisms stain readily with alkaline methylene blue 

 or gentian violet. Smith found in the acute cases that they 

 were most numerous in the blood from the capillaries of the 



fi Theiler. Report of the Government Bacteriologists. Pretoria, 

 South Africa, 1908-09. 



