Considering that Rh. evertsi is one of the most oommon ticks 
of the high-veld, although it is not found in such large numbers 
as in the low-veld, it became apparent that the disappearance 
of East Coast Fever from the high-veld had to be interpreted 
in a different way. 
The influence of cold as a possible factor in the destruction 
of the virus within the tick, suggested itself, and for this purpose 
experiments were undertaken with Rh. appendiculatus. 
Tn the first instance, it was surmised that on account of the 
considérable amount of liquid contained in engorged nymphae, 
this would be the stage more easilv affected by cold, and should 
it not prove to be the case, it was thought that as a sexual deve¬ 
lopment of the parasite probablv ensues within the tick, the cold 
might retard that sexual development, or else completelv înhibit 
it, in the same way as cold retards the development of the mala- 
rial parasite within the mosquito. 
At the same time it was decided to note the influence of cold 
on larvae of the blue tick, which are the sole survivors of the 
wînter months. 
Experiment N° i. — To infect a beast with East Coast Fever for the pur¬ 
pose of collecting engorged nymphae of Rh. appendiculatus. 
Cow 455. Infested on the 2^rd May 1907 with adults of Rh. evertsi, eol- 
lected from Ox 758 which at the time was suffering from East Coast Fever. 
Cow 455 died on the ryth June 1907, fram East Coast Fever. 
Engorged Rh. appendiculatus nvmphae were collected from Cow 455 
three davs hefore death (i4th June 1907). 
Experiment N° 2. ■— To prove that these engorged nvmphae of Rh. appen- 
diculatus will transmit East Coast Fever in their adult stage. 
The nymphae of Rh. appendiculatus which were collected on the i4th 
June, hatched on the i6th July, 32 days after they were collected. 
O .y 467, Infested on the 22nd October 1907, with adults of Rh. appendi¬ 
culatus from Cow 455. 
Piroplasma parvum was noted from the iSth to 2Tst days, on which latter 
date the beast was killed. 
Post Mortem examination shewed ail the lésions of East Coast Fever. 
Conclusion. — The adults of Rh. appendiculatus, which as 
engorged nymphae were collected from Cow 455, were capable 
of transmitting East Coast Fever. 
Experiment N° 3. — To note the effect of exposing engorged nvmphae of 
Rh. appendiculatus infected with Piroplasma parvum to a température of o°C. 
Some of the engorged nymphae of Rh. appendiculatus which had been 
