G. H. F. Nuttai.l and C. Strickland 
77 
II. PIROPLASMA (BABESIA) CABALLI. 
(A) The living parasites. 
Although tlie scarcity of parasites in the blood of the infected 
horses prevented our making as complete a study of their development 
in vivo as we should have wished, we nevertheless convinced ourselves 
that P. cahalli (Diagram VII) develops in a manner similar to P. bovis 
and P. canis. Small and medium-sized parasites are usually oval or 
rounded in shape ; they may, however, assume a somewhat piriform 
shape momentarily. When such parasites escape from corpuscles they 
degenerate and die. When large single piriform parasites occur in 
corpuscles (Diagram VII, D) they move about slowly in the corpuscle 
Diagram VII. P. cahalli. Illustrating living parasites observed in fresh blood-films at 
blood temperature. (Horse I, vi. 1910.) 
Fig. A. Two parasites, the larger, observed 15 minutes after the blood was drawn, almost 
developed into two piriform parasites at the end of 400 minutes. The smaller para¬ 
site underwent changes of form from round to piriform and oval. (G.H. F.N. del.) 
Fig. B. A single parasite: early stages of multiplication observed 35-53 minutes after 
the blood was drawn. (C. S. del.) 
Fig. C. Two conjoined piriform parasites showing changes of position within the cor¬ 
puscle during 10-42 minutes. (G.H.F.N. del.) 
Fig. D. Large piriform parasite slowly altering its shape and finally becoming rounded. 
The observation lasted 58 minutes. (C. S. del.) 
whilst retaining their piriform shape; as in P. bovis, some large 
piriforms may extend almost across jthe whole width of the corpuscle. 
When moving about, such piriforms may, occasionally appear rounded 
owing to their movements within the corpuscle being directed towards 
or atvay from the observer. Piriform parasites occurring in pairs were 
seen, as in P. canis, to escape from a corpuscle which afterwards 
vanished. Typical multiplication forms (Diagram VII, A and B) were 
seen as in P. canis and P. bovis, the “ buds ” persisting and leading 
almost to the complete formation of paired piriforms. The process of 
