G. H. F. Nuttall and S. TTadwen 
161 
single rounded parasite to give rise directly to four pyriform parasites 
by the “budding” process. (See Nuttall and Graham-Smith, 1907, 
p. 240, Diagram XXVII; 1908, p. 137, Diagram II, tig. 21.) The 
most reasonable explanation of the formation, under ordinary circum¬ 
stances, of four pyriform parasites (PPPP) in a corpuscle is the same 
as that which explains the presence of two rounded parasites (00) in a 
corpuscle, namely, that the corpuscle was originally invaded by two 
pyriform parasites which have undergone independent development 
side by side. It is our belief that the presence of larger numbers 
(6—12—16) of rounded and pyriform parasites within corpuscles, 
obtained especially in preparations taken from the internal organs, is 
due to the slowed circulation in those organs more freely permitting 
the entry of several pyriform parasites into adjacent corpuscles after 
they have escaped from the corpuscle in which they have accomplished 
their development. This does not exclude the occasional occurrence of 
the direct development of four or possibly more parasites from a large 
single amoeboid parasite. 
The proportion of rounded (0) to pairs of pyriform (PP) parasites 
varies somewhat in the same dog at different times; thus, in one of our 
untreated dogs (VIII), the proportion of (0) to (PP) was as 60 to 35 at 
one time, as 41 to 50 at another, the average proportion obtained 
from counts made on nine occasions, during a period of three days, being 
55 (0) to 39 (PP). 
If we calculate the proportion of (PP) to (0) parasites according to 
their percentage relation to each other, leaving less frequent forms out 
of account, we find that in control dog VIII for every 100 (0) parasites 
there were present 
On clay 7 
On day 5 Variation within 16 hours on day 6 when dog died 
°/o of (PP) to (0). 58 46 80 60 75 93 122 47 77 
°/ 0 of infected r.b.e. ? -6 ’4 1 2 1-2 2-8 17 28 
We shall see that the numerical relation between (0) and (PP) is 
much disturbed through the administration of the drugs in the experi¬ 
ments we are about to describe. 
The method of enumerating the different forms of intra- 
corpuscular parasites as recorded in the protocols. 
In consideration of what has been stated in the preceding section and 
of what is to follow, it will conduce to clearness and brevity to explain 
the signs used throughout this paper to indicate the different forms of 
intracorpuscular parasites which are encountered in the blood. 
Parasitology n 
11 
