PIROPLASMOSIS 677 



remainder of the parasite consisting of blue-staining basophilic substance. 

 The parasite is surrounded by a non-staining refractile capsule, one-sixth 

 of the diameter of the parasite in width and sometimes containing a 

 single minute chromatoid dot, and similar granules are sometimes seen 

 in the non-chromatoid part of the body of the parasite. Darling considers 

 this organism to be diiferent from the Leishmania donovani in the form 

 and arrangement of its chromatin and in not possessing a blepharoplast. 



Pikoplasmosis. 



Up to the present no human disease has been proved to be associated 

 with the presence of piroplasmata. But several important diseases of the 

 lower animals are almost certainly caused by protozoan parasites of this 

 group, and a short account 



of the organisms may be __ ■ 



given. 



The piroplasmata are 

 pear-shaped unicellular or- 

 ganisms about 1 to l - 5 /j. 

 long and varying in 

 breadth. The peripheral 

 part is denser than the 

 central, which often ap- 

 pears as if vacuolated, and 

 at the broad end there is 

 a well-staining chromatin 

 mass. Sometimes irregular 

 and ring-, rod-, or oval- 

 shaped individuals occur. 

 The organisms are found 

 within the red blood cor- 

 puscles of the infected 

 animal and also free in 

 the blood. In the former 



situation there is some- ^ IG - 200. — Histoplasma capsulatum, section of 

 times only one within a liver - xl00 °- 



cell, but the numbers vary 



under different circumstances and in different species. Multiplication 

 takes place by fission, and the new individuals, remaining for longer 

 or shorter times in apposition, account for some of the appearances 

 seen in cells. Especially in the forms free in the blood, pseudopodial 

 prolongations of the protoplasm, usually from the pointed end, are 

 developed, and it may be by means of such pseudopodia that entrance to 

 the red cells is obtained. Infection is usually carried from infected 

 animals by means of ticks. In one case Koch has described the develop- 

 ment in the organism, in the stomach of the tick, of spiked protoplasmic 

 processes sprouting out from the broad end of the piroplasm, and the 

 occurrence of conjugation of two such individuals by their narrow ends 

 to form a zygote. Observations by Christophers indicate that a globular 

 ibody now appears, probably corresponding to the oocyst stage of other 

 similar protozoa, and the further development consists in a division into 

 sporoblasts which may infect the whole tissues of the tick, especially the 

 Salivary apparatus. The eggs may also be infected, and the young ticks 

 developed from these may thus be capable of carrying the disease to 



