PIROPLASMA MURIS. 501 



. . . purely conjectural/') Nor do these easily fit in with 

 Koch's recent researches on P. bigeuiinum in the tick (21). 



In sections of the internal organs^ as the liver and kidneys, 

 infected corpuscles are seen to be numerous in the capillaries 

 (fig. 23). Endogenous reproduction of the parasite would 

 appear to be especially prevalent in these parts. 



Regarding the sporogony of P. muris, I have, unfortu- 

 nately, no observations, nor, indeed, have any well-authenti- 

 cated details been published by any observer on the exogenous 

 reproduction of any species of Piroplasma, with the possible 

 exception of a preliminary note by Lingard and Jennings 

 (33) on Piroplasmata in Mammals and even birds and 

 lizards (!), wherein figures of what purport to be sporogony 

 (" sexual ") stages are given. This account by Lingard and 

 Jennings, although avowedly preliminary, is, unfortunately, 

 somewhat condensed and disconnected, and so not very clear. 

 Information on the sporogony of many, indeed most, of the 

 Hsemosporidia is still wanting. 



With respect to the dissemination of piroplasmosis among 

 white rats little can at present be stated. I carefully searched 

 the infected rodents for ticks, but found none. Lice were 

 abundant on one rat, and fleas also occurred, but no clearly- 

 defined further stages of the Piroplasma were seen in the 

 internal organs of these insects. The 'intermediate" (in- 

 vertebrate) host is probably a tick, as has been shown in all 

 other cases of true piroplasmosis hitherto examined. The 

 three rats infected with P. muris and discussed in this 

 memoir were, I understand, obtained from two separate 

 sources in the East-end of London, but as to the manner 

 in which they became infected in the first instance I have no 

 information. 



Very few examples of phagocytosis of the parasites were 

 observed. One or two instances of apparently free parasites 

 being engulfed by leucocytes were noticed (fig. 22), but no 

 cases of leucocytes actually destroying infected erythrocytes 

 could be detected. The paucity of examples of phagocytosis 

 has been emphasised by other observers of Hsemosporidia. 



