1 Dzc., 1898.] QUEENSLAND AGRICULTURAL JOURNAL. 455 
Tt has to be stated, however, that marked protection—or immunity, as it 
sometimes called—has, in some instances, been proved to follow the injection 
of “recovered blood,” even when it has produced no discernible reaction. 
This circumstance has, I think, been more probably due to some quality or 
substance of an antifovic kind in the blood of the recovered animal than to 
the presence of the specific micro-organisms. And the immunity produced has 
been of a “passive” kind, and therefore almost certainly of short duration. 
But, leaving out such exceptional cases (which suggest a most interesting field 
for further study), I am confident that, in a general way, the degree of 
permanent immunity conferred against Texas fever—as in the case of inocula- 
tion for smallpox and other diseases—is very closely related to the amount of 
reaction produced; and Dr. Edington has remarked the same thing in con- 
nection with inoculation for rinderpest in South Africa. 
One of the practical difficulties we have to encounter—especially in the 
inoculation of such highly susceptible animals as aged bulls—is to produce 
sufficient reaction to insure subsequent immunity, without producing so much 
as to endanger the life of the animal. For we have as yet no satisfactory 
means of regulating the amount of reaction. Safety has been thought to lie 
in the injection of very minute doses, but this idea has not been completely 
substantiated. Pretty heavy losses have been reported in bulls that have been 
inoculated under favourable conditions on their own pasture with only L'cc., or 
about 20 drops, of “recovered blood.” Tf any security at all lies in small 
doses this quantity must therefore be regarded as above the limit of safety for 
such animals. Bulls have been safely and satisfactorily inoculated with only 
10 drops, but this fact alone does not help us much, as the same result has 
also been attained in other instances where much larger doses have been used. 
Only careful comparative experiments on a large scale, such as might well be 
undertaken at the joint expense of all the colonies interested, can definitely 
settle this question. 
I must not, however, digress into a discussion of the problems connected 
with this subject, and the various experiments that have been undertaken to 
solve them... There still, undoubtedly, remain many questions to occupy the 
attention of those who may be charged with the duty of unravelling —or 
attempting to unravel—them. In what I have said, I have endeavoured rather 
to lay before you the principles upon which the practice is based than to 
advocate it as a sort of fetish which, like a pink pill or a bile bean, 1s to be 
blindly accepted. It is perhaps hardly necessary for me to remind you that 
inoculation is a protective against Texas fever, not a cure, for it; and that 
is the height of folly to postpone the operation till the disease is actually 
devastating a herd, and then, as some of my acquaintances have done, abuse 
inoculation as useless—deadly—and the cause of all the mischief. 
Tn conclusion, may I be allowed to offer you a word of congratulation, in 
that from all [ can gather the cattle remaining in your district are now pretty 
well through with the fever, and you with the trouble ? Fortunately, the evils 
which ticks do are comparatively short-lived, and herds over which the disastrous 
wave has already passed arein no way permanently injured, and live and thrive 
and multiply as well as ever. We see this already in some of the Northern 
parts of Queensland, not to speak of o‘her great cattle-raising countries where- 
ticks are constantly present. I had lately an opportunity of inspecting one of 
the largest dairy herds in the Central district, which within the last two years 
has passed through the very severest ordeal of the tick plague, and where the 
paddocks are still virulently infested, ‘so that susceptible cattle placed there 
contract the fever with the greatest precision—and even cattle that have been 
.rendered immune by inoculation against the fever are greatly worried and 
worn down for a time when first brought ints them. Yet thig herd is now a 
very picture of health. The cows are sleek, fat, and practically tick free ; and 
their yield of milk is, in quality and quantity, all that could be desired. They 
haye emerged from the ordeal quite uninjured. : 
