PIROPLASMA MURIS. 503 



more numerous in the iuterual organs^ such as the liver 

 spleeUj kidneys, heart-muscle, lung, and bone-marrow, espe- 

 cially in the capillaries of these, which were enlarged. In 

 the liver, and to some extent in the kidneys, the outlines of 

 the cells were not easily apparent or were even broken down, 

 the cytoplasm was ill-defined, and the nuclei of the hepatic 

 cells were often hypertrophied (fig. 23). 



Probably most, if not all, of the symptoms outlined above 

 are those of piroplasmosis, judging from published accounts 

 of cases of the disease in other mammals. 



It would be interesting to determine if the disease is 

 periodic ; possibly it occurs in the spring or early summer. 

 Information is also required, as already remarked, regarding 

 the invertebrate host, probably a blood-sucking Arthropod, 

 which may be concerned in the spread of the disease. 



Further, the disease may not be strictly limited to the 

 white rat, that is, the albino variety, but will perhaps be 

 found in black (Mus rattus) and brown (M. decumauus) 

 rats. 



Cultures of infected blood, made bj^ adding sodium citrate 

 and a little citric acid to freshly drawn blood, showed no 

 further stages or development of the parasite, even after 

 several days. 



VI. Systematic ; the genus Pikoplasma. 



Summarising briefly some of the more important charac- 

 teristics of the parasite '^ already described, we notice the 

 usually ovoid or pyriform shape of the trophozoite, generally 

 with a single well-marked chromatin dot, multiplication by 

 binary fission into two merozoites, the absence of melanin 

 pigment, and the cytozoic habitat within a red blood-cor- 

 puscle during the endogenous stages. From these features 

 it may be concluded that the parasite is a Hajmosporidian, 



' The sizes of tiie various forms of the parasite are given on pp. 498 and 508. 



