Annals of the Transvaal Museum. 
245 
placed at my disposal at the Government Veterinary Bacteriological 
Laboratory, for protozoological studies, amounting to about 80-100 head 
of cattle used in East Coast fever experiments, I frequently had the 
opportunity of controlling my observations. 
In the intracellular forms it occasionally happens that through the 
dissolution of the lymphocyte, these escape and invade the blood corpuscles 
as gamonts. It also sometimes occurs that very small free gamonts are 
seen in the lymphatic glands, etc., which, without reaching any great 
size, divide into gametocytes. Such small gamonts can finally further 
divide into gametocytes in the blood corpuscles, but I very rarely succeeded 
in tracing their development in the blood. Mistakes can easily occur, 
since the parasite very rapidly leaves the corpuscles when the blood is 
brought into different physiological conditions— a fact which can also be 
noted under the microscope. The formation of “ cross-forms ” as a rule 
takes place in the organs. 
The gametocytes in the blood are sufficiently well known, as is also 
the rapid increase of their numbers. With such a heavy infection of the 
blood, one is struck with the fact that no pathological lesions are found 
in the red corpuscles, and only towards the end of the disease may a slight 
anisocytosis be observed. If a further development, or rather if an increase 
would take place in the blood, one would expect to find changes in the 
red corpuscles such as are found with the malaria-plasmodia of apes, 
parasites found in bats, Babesia mutans, etc., either due to the liberation 
of the toxines, or by the simple mechanical influences caused by immigration 
and emigration of parasites into and out of the corpuscles. In the stages 
of the East Coast fever parasite found in the blood, we do not notice such 
changes of the corpuscles, and the absence of such changes Gan be explained 
by the life-cycle as explained before. With the formation of the gameto- 
cytes, the cycle of Theileria parva in the animal arrives at a definite 
conclusion — the animal either recovers or dies. 
In cattle which recover from the disease, a general decrease of the 
parasites is noted in the blood after the crisis. The agamogonous forms 
disappear, and with this the fever gradually subsides. The gamogonous 
stages do not develop beyond the formation of gametocytes, these are 
the endoglobular parasites. Since we do not find parthenogenesis, the 
animal is completely protected against relapses, and recovery leaves a 
complete sterile immunity. No tick can infect itself on this animal and 
no infected tick can infect such a beast. 
In my studies I also had an opportunity of seeing cases ending rapidly 
with death (acute forms of East Coast fever), in which I could not detect 
any parasites in the blood or gamogonous forms in the glands, but only 
the agamogonous stages. Therefore I am of opinion that in the first 
Instance agamogonous forms are those which cause the disease, or which, 
in other words, possess the toxines. In some of the experiments of 
Doctor Theiler, undertaken for the purpose of immunizing cattle, I have 
noticed agamogonous stages in the blood after inoculation, and it may 
be expected that these animals will prove immune to the disease. 
