120 
Theileria parva 
Forms apparently undergoing division into four :—In the blood films 
taken, especially in the later stages of the disease, we not infrequently 
encountered parasites containing four masses of chromatin lying 
in distinctly blue-staining cytoplasm (fig. 47), or apparently projecting 
(fig. 4S) from a small mass of indistinctly staining cytoplasm. These 
may be referred to as true “cross-forms.” Fig. 81 perhaps represents 
a parasite which has broken away from such a cross-form, three masses 
of chromatin being left in the remaining cytoplasm. At times, more 
particularly immediately before the death of the host, irregularly formed, 
possibly amoeboid, parasites were seen which contained three (fig. 46; 
note vacuoles) or four (fig. 45) masses of chromatin. 
Free parasites were rarely encountered in stained films ; those that 
were observed were ovoid or bacilliform. We have occasionally observed 
them in fresh blood, as noted elsewhere ( Parasitology , vol. n. p. 338). 
The relative numbers of different types of parasites. 
In the following tables we give the results of some counts in which we 
attempted to classify the parasites according to types. For this purpose 
we usually examined 250 corpuscles in each film and noted the kinds and 
numbers of parasites which occurred in them. We do not include the 
rarer types of parasites in the tables. The numbers beneath the 
bracketed signs indicate, in round figures, the percentages of different 
parasites present in the peripheral blood on succeeding days. It was 
soon found to be very difficult to classify parasites under the various 
types, since intermediate forms (for instance between bacilliforms and 
comma-forms) were encountered; nevertheless, an arbitrary division was 
made, and the results appear worth recording. 
In the signs used in the tables the brackets ( ) represent corpuscles 
which include the parasites. Thus : 
The signs 
stand for a corpuscle harbouring 
(0) 
1 round or ovoid parasite. 
(.) 
1 drum-stick or comma-shaped parasite. 
(1) 
1 rod-shaped parasite. 
(o) 
1 thick bent sausage-shaped parasite. 
(00) to (III) 
2 to 3 rounded bacilliform etc. parasites 
the preceding signs. 
(3) 
Groups such as (001), (00,), (Oil), (,ll). 
(OJ, (h) 
4 rounded or rod-shaped parasites. 
(5-6) 
5-6 parasites of various types. 
The day of illness is reckoned from the time when the pathogenic ticks were placed 
upon the cows. 
