160 
The Cure of Piroplasmosis 
Note upon the development of Piroplasma canis in 
untreated dogs. 
Before proceeding to describe the very striking effects exerted by 
Trypanblau and Trypanrot upon the parasites, it appears expedient 
to refer briefly to the mode of development of P. canis. 
For a clearer understanding of the significance of the forms of 
parasites to which we shall refer in this paper, we reprint a Diagram 
from Nuttall and Graham-Smith ( Journ. of Hygiene, 1907, vil. p. 257), 
wherein is represented the usual mode of multiplication of Piroplasma 
canis in the circulating blood. The figure is based upon extensive 
studies of the living parasite, supplemented by the examination of 
stained specimens. 
In this Diagram the figures are numbered successively 1 to 15 
and represent the stages in the life history of the parasite whose 
significance is explained in the description of the Diagram (p. 158). 
A consideration of the cycle of development described and 
figured in the Diagram, readily explains the reason for the presence 
of two prevailing forms of intracorpuscular parasites. Free pyriform 
parasites are rarely encountered except toward the end of a fatal 
attack of the disease, when the corpuscles rapidly break down and 
haemoglobinuria is a prominent and consequent symptom. The reason 
for there usually being few free pyriform parasites is due to the fact that, 
immediately upon their escape from the corpuscle in which they have 
developed, they re-enter fresh corpuscles. As a rule, few single pyriform 
parasites are encountered within corpuscles, because after they have 
penetrated the corpuscle the parasites very soon become rounded. 
Similarly, the dividing forms, which have been overlooked by other 
observers, are not commonly encountered except in small numbers 
because the process of division is fairly rapid. At times dividing 
forms are more plentiful than at others. Some striking figures in 
this respect can be seen by reference to those of our protocols which 
include an enumeration of the different forms of parasites encountered 
in blood films at various stages of the disease. 
The two prevailing forms of intracorpuscular parasites are (0), the 
single rounded or irregular (amoeboid) parasite, and (PP), the pairs of 
pyriform parasites. These two forms prevail because they represent 
phases of development which progress slowly. That two pairs of 
pyriform parasites (PPPP) occur more rarely is due to the fact that 
a rounded parasite usually developes into two pyriform parasites by 
the process figured in the Diagram; it is a rare occurrence for a 
