Gr. H. F. Nuttall 
419 
enumeration on the 11th day showed that 324 °/ 0 (morning) and 19'2 °/ 0 
(afternoon) of the r. b. c. were infected. Nevertheless, the number of 
(PP) forms had fallen to 19 °/o and 8°/o respectively. On the 12th day 
the percentage of infected r.b.c. continued to fall, and only 1 °/o of (PP) 
forms were encountered in the afternoon. On the 13th day only rounded 
parasites were encountered. On the 15th to 24th days no parasites 
could be detected, after which they reappeared and the dog died of piro- 
plasmosis, the percentage of infected r.b.c. in the peripheral circulation 
being low (2 °/o), whilst high counts (6 to 15 °/ 0 ) were obtained from 
smears of the internal organs. 
In Dog 5 the parasites appeared on the 8th day after inoculation 
and the dye was injected on the 9th day. Here the percentage of 
infected r.b.c. rose very slightly on the 10th day, whilst the number 
of (PP) forms decreased to 19 °/ 0 and 3°/o in the morning and afternoon 
enumerations. On the 11th day only rounded parasites were en¬ 
countered and no parasites were found after the afternoon of the 12th 
day. At autopsy, on the 15th day, only a very few parasites could be 
detected in the dog’s internal organs. 
N.B. It is necessary to repeat, in this connection, that in dogs which 
recover normally from piroplasmosis the behaviour of the parasites is 
quite different to that observed in dogs treated with trypanblue, 
trypanred, or Congo Red. Whereas, in normal recovery, whilst the 
percentage of infected corpuscles gradually decreases, the pyriform 
parasites persist as long as parasites are discoverable microscopically. 
On the other hand, after effective dye treatment, the percentage of 
infected corpuscles falls rapidly and the pyriform parasites disappear. 
It is essential, therefore, when experimenting upon the possibly 
curative effect of such remedies to make accurate counts of the different 
types of parasites found in the peripheral blood of the experimental 
animals both before and after treatment. 
3. The Continued Infectivity of the blood of dogs which have 
recovered from Piroplasmosis after Treatment with Trypan¬ 
blue and Trypanred. 
In a previous paper (Nuttall and Hadwen, vi. 1909; this volume, 
pp. 172, 176, 177, 180) the cases of 4 dogs were described which had 
survived an attack of piroplasmosis consequent upon treatment. The 
dogs (Nos. 1, 3, 4 and 6) appeared quite well at the time we published 
the account of our experiments. Whereas some of our other dogs, 
