258 H. M. WOODCOCK. 



It is also uncertain whether the infection of the leucocytes 

 is an active or a passive one. The opinion has been 

 expressed that the host-cells, in their phagocytic capacity, 

 ingest the parasites — if so, verily a case of the " biter bit." 

 On the other hand, if the parasites enter the cells when in 

 a Flagellate phase (as e.g. T. ziemanni penetrates the 

 leucocytes of the owl) it is more likely an instance of active 

 infection, the organisms being especially adapted to that kind 

 of cell — '^Leucocytozoa" in fact. Nevertheless, it appears 

 highly probable that the parasites are not exclusively limited 

 to such a habitat, but that they also attack red blood- 

 corpuscles as well, being also, therefore, in that respect, true 

 Ha^mosporidia. Both Laveran and Mesnil and Donovan 

 describe and figure them as endoglobular, and great 

 weight must be assigned to the view of the first-named 

 investigators. Moreover, the figures of Donovan (I. c.) are 

 sufficiently convincing; and, having regard to the unmistak- 

 ably Fir op las ma-like facies which the organisms at times 

 possess, the rod or comma-forms depicted (fig. 37 I e) strongly 

 recall the " bacillary " type of F. bigeminum in a similar 

 situation (see Laveran [34]). Lastly, Donovan has observed 

 the parasites in the peripheral circulation, although only 

 rarely and duriug periods of high fever; and Laverau, who 

 has examined his preparations, confirms this observation. 



There is little additional to be noted concerning the 

 habitat of the localised parasite (Wright's ulcer form). 

 This also is either free or intracellular; in the latter case 

 it is j)arasitic in the ulcer cells and in the large migratory 

 corpuscles (phagocytes), which doubtless correspond, in part, 

 to the macrophageal cells of the other type. Mesnil, 

 Nicolle, and Kemliuger (137) have seen, in sections, multi- 

 plication forms, both free and intracellular. 



The parasites themselves are very minute, and appear 

 rounded, ovoid, or pyriform in shape (fig. o7) ; the tyj)ical 

 form may very well be that of a slightly fiattened pear. The 

 splenic form is somewhat smaller than Wright's parasite, 

 aud this is about the only visible distinction between the 



