310 SPOEOZOA. 



The larger chromatin granule also now divides, followed by 

 the division of the cytoplasm, and two pear-shaped merozoites 

 result (fig. 150, H-J). These merozoites may now leave the 

 corpuscle to invade other corpuscles or may further divide 

 within the same corpuscle so as to produce multiple-cell 

 infections. Schizogony is thus by budding, and is not com- 

 parable with that of the malarial parasites. Sometimes 

 there may be as many as sixteen of these organisms in a single 

 blood- corpuscle . 



The Cycle in the Tick. — When ingested into the stomach 

 of the tick the parasites leave the blood- corpuscle, increase 

 in size, and become globular bodies, 4-5 /a in diameter. A spHt 

 appears in the globular body, a portion swings round, and the 

 globular body is changed into a club-shaped body. The club- 

 shaped bodies are motile and Gregarine-hke. Whether any 

 sexual process is involved is not known. The club-shaped 

 bodies, after passing through the wall of the gut, enter the 

 ova and later are found in the tissue -cells of the embryo 

 developed from the egg. There they again become globular, 

 and increase in size up to a diameter of 25 /x. This globular 

 stage, termed " zygote " by Christophers, according to 

 Minchin probably corresponds to the oocyst of the Plasmodiidae. 

 The globular body divides up by multiple fission into a number 

 of " sporoblasts," which do not remain aggregated together, 

 but scatter themselves through the tissues of the tick, larva, 

 nymph, or adult as the case may be. The nucleus of each 

 sporoblast divides into a large number, and then the sporoblast 

 segments into an equal number of sporozoites, which are 

 small bodies with a single nucleus similar in appearance to 

 the forms in the blood. The sporozoites collect in the sahvary 

 glands of the tick and pass into the blood of the dog when the 

 tick next feeds on it. 



Remarks. — The parasite was first discovered as the cause of 

 malignant jaundice of dogs in Italy, and has since been shown 

 to have a wide distribution. It has long been known to yield 

 to treatment with the aniHne dye, trypan blue. Lingard and 

 Jennmgs (1904), James (1905), Webb (1906), and Christophers 

 (1907 a, 1907 h) were the earliest to study it in India. Christo- 

 phers showed that in India JRhipicephalus sanguineus (LatreUle) 

 was the transmitting tick, and described the cycle in the tick 

 as summarized above. Christophers also proved that eggs 

 laid by an adult which had fed on infected dogs gave rise 

 to larvae which were not infective, but that the nymphs, 

 and probably the resulting adults, were infective. James 

 took specimens of R. sanguineus to England and succeeded in 

 infecting English dogs with them. Baldrey (1911) gave 

 a useful summary of the observations on piroplasmosis in 

 India up to that date. 



