" Anaplasma Marginale' 
71 
blood of two animals which succumbed to the disease. A second lot of 
ten heifers, which were all immunised in the same way in London, were 
not exposed to natural infection after their arrival, but inoculated a second 
time in the Transvaal with blood containing P. higeminum. The result 
was that this inoculation did not break the immunity against Eedwater. 
After a certain period, varying in length from twenty-seven to thirty-two 
days, a typical fever reaction commenced, which was initiated and 
accompanied by the presence of marginal points. Of ten animals 
injected five died. It was evident that P. higeminum was not responsible 
for this disease. With the inoculation of the blood two different parasites 
had been injected — P. higeminum, against which the animals were immune. 
Anaplasma Marginale. 
and another one, the marginal points, which caused the disease. If this 
conclusion was right it had to be expected that it would be possible 
to separate these two parasites, at least to isolate the one with the shorter 
incubation time. It was indeed possible to do so with P. higeminum, 
whose incubation period is the shorter one. A pure infection resulted 
after injections of blood, taken at the beginning of the acute attack of 
Eedwater, into a susceptible beast. When this animal, at a later period, 
was infected with marginal points, it promptly reacted to this infection. 
The reverse experiment was not so easy, because wherever we had an 
infection with marginal points it was complicated with P. higeminum, so 
