xxviii Transactions of the Royal Society of South Africa. 
East Coast fever aad which had transmitted the disease in their nymphal 
stage, were no longer infective for susceptible cattle. Four batches of 
ticks proved their infectivity in the nymphal stage on eight animals, but 
in their adult stage failed to transmit the disease to two susceptible 
animals. 
(2) Ticks belonging to the same batches which were feeding on two 
animals rendered immune to East Coast fever by inoculation, in the 
nymphal stage, did not transmit the disease in their adult stage to six 
animals, thus proving that the brown tick which has become infected in 
one stage, cleans itself in the following stage by feeding on an immune or 
susceptible animal. 
(3) Ticks which became infected with East Coast fever in their larval 
stage, and which passed their nymphal stage on a rabbit, did not prove to 
be infective in their adult stage for susceptible cattle. This conclusion 
bears out that given above (2), showing that a tick loses its infectivity the 
first time it feeds on an animal susceptible or immune to East Coast fever. 
(4) Clean or infective ticks feeding on an animal which has recovered 
from an attack of East Coast fever do not transmit the disease in their 
next stage. This conclusion is in support of experiments undertaken 
eight years ago [vide Annual Eeport of the Government Veterinary 
Bacteriologist, 1904-5). 
(5) It has been demonstrated that certain batches of ticks collected at 
the same time and which fed under similar conditions did not transmit 
the disease in their next stage, even when infected in great numbers and 
on numerous animals. Other batches of ticks reared in exactly the same 
way and under similar conditions only infected a few animals, whilst again 
other ticks proved infective in almost every instance, even when a mini- 
mum number were used. 
It is difficult to give an explanation of this fact, but it is quite likely 
that outside conditions have some influence. The ticks which did not 
transmit the disease were bred during the coldest time of the year. This 
may perhaps explain the fact that during the winter months the infection 
in the field is not so active as during the summer months, remembering at 
the same time that during the winter months tick life is generally weaker 
than in the summer. 
Ordinary Monthly Meeting. 
October 18, 1911. 
The Vice-President, H. H. W. Pearson, in the Chair. 
Nomination : D. Sutherns, B.A., Natal, by C. Stewart and L, 
Peringuey. 
