84 QUEENSLAND AGRICULTURAL JOURNAL. [1 Jury, 1899. 
This complex process of the alternation of generations of the micro- 
organisms of tick fever has been engaging my attention for some considerable 
time, and from my observations I feel more and more confident that this is the 
only satisfactory explanation why there are so often long pone of time intervening 
between the first appearance of ticks and an outbreak of the disease, and also 
why the disease suddenly disappears and subsequently reappears with the 
same amount of virulence at a later date. In other words, although tick- 
infested cattle have the micro-organisms in their blood, and all ticks carry the 
micro-organisms, which are transmitted through the ova to the larval tick, it does 
not follow that these micro-organisms are pathogenic. This has been proved 
repeatedly as a result of the examination of blood of long tick-infested cattle at 
ount Cornish, Boolburra, and other centres, where the organisms in certain 
stages were extremely numerous, but without causing any apparent injury to 
the elements of the vascular system. The reproduction of these non-pathogenic 
forms may go on through a great many successive generations—first through 
the tick, then through the cattle, and so on backwards and forwards until a 
time arrives when some of the cells (organisms) club together and form, as it 
were, gemmules, from which the red corpuscle-destroying form of micro-parasite is 
developed. 
EXPERIMENTS IN PROGRESS WITH THE VIRULENT BLOOD 
TAKEN FROM THE DEAD AYRSHIRE COW. 
In order to ascertain— 
1. How long immunity will last after recovery from natural tick fever ; 
2. For what period an animal will remain immune after recovery from 
inoculation with recovered blood ; 
8. Whether a calf, whose blood immediately after birth produced severe 
tick fever when injected into a number of healthy cows, is immune 
to the effects of an injection of virulent blood; 
the following animals each received a hypodermic injection of 10 c.c. of blood 
taken from the dead cow “ Annie” :— 
One of the original Inkerman steers that was obtained from North Queens- 
land in February, 1897. 
Two cows that had recovered over 24 years from natural tick fever, and 
were sole survivors of a dairy herd that had all died from acute fever. 
One heifer that had been inoculated direct from the original Inkerman 
steer in February, 1897 (2 years and 4 months ago). ; 
One Shorthorn bull that was inoculated from an animal, the fifth remove 
from the Inkerman steer. 
One heifer calf, 3 months old, uninoculated, but born of the heifer (referred 
to above) that had been inoculated over 2 years. 
NOTES ON TICKS AND INOCULATION AT ST. HELENA. 
At St. Helena we have the most conclusive evidence that the first ticks that 
got on to the cattle were the progeny of ticks that matured on sheep which, 
coming from tick country, were taken down to the island about 8 months ago. 
Two months later, on 18th January, all the cattle, with the exception of twelve 
milking cows, were inoculated. On 28th March, the animals which had been 
previously operated upon’ were again inoculated, together with six of the 
uninoculated milking cows. The remaining six uninoculated cows have since 
been freely mixing with the inoculated cattle, and ticks have been and can 
always be found on every animal in the herd; yet, strange to say, up to the 
present time, not one of the uninoculated cows have shown the slightest 
symptoms of fever or sickness, nor has any diminution occurred in their milk 
supply. If, however, tick fever should develop among the uninoculated 
animals, the case will be much more interesting than the Indooroopilly one, 
from the fact that we are certain that before the first ticks attached themselves 
