PIROPLASMA BIGEMINUM 515 



and takes a darker stain. \Vitliin the largest forms in the centre of the 

 thick end is a large round or oval body, 0.5/* to I//, which sometimes 

 shows amo'boid motions. The motion of the whole parasite on the warm 

 stage is not produced by the formation of distinct pseudopods, but by a 

 constant change of the boundary. The changes can succeed each other 

 so quickly that it is scarcely possible to follow them with the eye. The 

 motion may persist for hours. The single ones show motion, while the 

 double ones remain unchanged. f The parasites take most basic aniline 

 stains well. Methylene blue is especially recommended. The Roman- 

 owsky method or its modifications gives the best results. 



The number of red cells infected is about 1 per cent, of the whole. 

 If the number increases to 5 per cent, or 10 per cent, it generally means 

 the death of the animal. The parasites quickly disappear from the 

 blood after the disappearance of the fever. In fatal cases many para- 

 sites are found in the red blood cells of the internal organs. They 

 vary in number according to the stage at which death occurs, are most 

 abundant in the kidneys, and are found in fewer numbers in the liver, 

 spleen, and other internal organs. 



The complete life cycle of the organism is not known. According 

 to Smith and Kilborne tiny motile spore forms enter the red blood cells 

 and divide, the two parts remaining together forming diplococcus-like 

 bodies. These forms increase in size and produce the pear-shaped 

 bodies. How the small forms are produced from these is not known. 



R. Koch has described a bacillar form which he found in large num- 

 bers in red blood cells of acute fatal cases in' East Africa. Between 

 these and the pear-shaped forms he found all grades. He considers 

 them young forms. 



Ziemann showed by the Romanowsky method that the parasite con- 

 tained chromatin staining material situated at or near its periphery. 



Kossel and Weber, who studied the parasite found in haemoglobinuria 

 of cattle in Finland, give the following description of the specimens 

 stained according to Romanowsky: 



" The smallest forms appear as tiny rings, about one-sixth the diameter 

 of the red blood cell. The rim of the ring takes the red stain, while the 

 rest appears blue. Forms a little larger are irregular in outline and 

 already show an arrangement of the chromatin into two parts, which 

 are more distinct in larger parasites and which finally become separated 

 into four parts. In the large, double, pear-shaped parasites the chro- 

 matin is generally situated at the poles, more seldom near the middle." 



No division forms similar to thos? seen in the sporulating stage or schiz- 

 ogonv in malaria have been seen. Neither has a sexual cycle in another 

 host similar to thatof the malarial parasite in the mosquito been observed. 

 Smith and Kilborne showed that the infection is caused by the larva of 

 a species of tick, Boophilus bovis Curtis (rhipicephalus annulatus), and 

 Kossel gives Ixodes redivius as the tick causing transmission of the germ 

 in the hremoglobiniiria of Finland cattle. We know nothing of any 

 changes going on in the parasite in its passage through the tick. The 

 ticks feeding upon the blood of cattle and other mammals become 



