THE ILEMOSPORIDIA 



383 



The piriform parasites escape from the corpuscle when it is exhausted, 

 and approach other corpuscles, moving with considerable rapidity. The 

 parasite attacks the corpuscle with its blunt extremity foremost, and " rapidly 

 indents its surface. Then violent movement of the thin end of the parasite 

 occurs, and the side of the corpuscle becomes greatly distorted. . . . Gradually 

 the parasite sinks more deeply into the corpuscle, and finally disappears within 

 it, when the movements of the corpuscle cease and it resumes its rounded 

 shape " (Nuttall and Graham-Smith, 748, vi., p. 235 ; compare the penetra- 

 tion of blood- corpuscles by Lankesterella described above). Only piriform or 

 long parasites enter corpuscles, never the round forms but immediately after 

 its entry into the corpuscle the parasite becomes rounded. If rounded para- 

 sites are set free from a corpuscle by its rupture, they die off, as do also the 

 pear-shaped forms if they do not succeed in penetrating into a corpuscle. 



FIG. 161. Diagrams showing the mode of division of Piroplasma cania in the 

 blood-corpuscle. A, Parasite about to divide ; B, the nucleus budding off a 

 smaller mass ; C, the nuclear bud has grown out into a forked strand ; D, the 

 forked ends of the strand are growing out into protoplasmic buds ; E, F, O, 

 growth of the buds at the expense of the main body ; H, I, J, final stages of 

 the division of the body. After Nuttall and Graham -Smith. 



A peculiar parasite, perhaps allied to the true piropasms, is Anaplasma 

 marginale, which occurs in the blood of cattle, and causes a disease charac- 

 terized by destruction of the red corpuscles and production of high fever, 

 leading to a degeneration of the large parenchymatous organs. The parasite 

 occurs within the red corpuscles, and is described as consisting solely of 

 chromatinic substance, without a cytoplasmic body; hence the parasites 

 were formerly described as " marginal points." The parasite has the form 

 of a round or oval coccus-like body which multiplies by simple fission. It is 

 transmitted by a tick, Rhipicephalus decoloratus. See especially Theiler (752). 



The transmission of piro plasms was first discovered by the 

 American investigators Smith and Kilborne, who in a classical 



