72 
Equine Piroplasmosis 
(4) Dividing forms : In a number of cases stages of development 
of a single parasite into four were observed, and the four young parasites 
were seen to separate. In one case (Diagram V, A) a previously 
rounded parasite was seen to give rise to four parasites after developing 
into a “ cross-form.” In most cases the cross-forms break up into four 
distinct parasites which wander away from each other. In three cases, 
what appeared to be an ordinary cross-form, gave rise to five parasites 
(Diagram V, B), and in one case six parasites resulted from the process 
of division (Diagram V, C). Young parasites, soon after they separate, 
may be very active and move about within the corpuscle (Dia¬ 
gram V, D). 
In a few cases multiplication occurred by a budding process 
(Diagram V, E and F). Appearances may well be deceptive in such 
cases, for at times, when the infected corpuscle ruptures, the main mass 
of the parasite’s protoplasm is seen to be connected to the supposed 
daughter individuals by delicate strands of protoplasm, which, owing 
to the haemoglobin within the corpuscle, had previously been in¬ 
visible. 
(5) The escape of young parasites from corpuscles was observed in 
a number of instances to occur shortly after they had become separated, 
the young parasites having arisen from a cross-form. The parasites did 
not rupture the corpuscle in the act of escaping. Immediately after 
their escape, singly or all together, the parasites appeared ovoid or 
piriform ; they at times swam about actively for a few moments, after 
which they usually vanished, the conditions in vitro being doubtless 
unfavourable to their continued existence. Although we are convinced 
that the young parasites under natural conditions immediately re-enter 
fresh corpuscles after the manner of Piroplasma, we did not actually 
succeed in observing their entry into another corpuscle. The minute 
size of the parasites left us in doubt as to whether they lay upon or 
within the fresh corpuscle. On one occasion we saw a medium-sized 
parasite escape and degenerate outside the corpuscle which it left 
uninjured. It was noted several times in observing the microscopic 
field that the first corpuscles whose contained parasites escaped were 
those that harboured four young parasites. Some of these corpuscles 
vanished whilst the contained parasites appeared to be motionless, in 
other cases the corpuscles burst suddenly and the parasites were all 
ejected into the plasma. 
