452 QUEENSLAND AGRICULTURAL JOURNAL, [1 Drc., 1898. 
germs from their parents, they must, of necessity, have acquired them de novo 
in such localities. And, in that case, there can be no ground for regarding the 
disease as one of coastal origin. As a matter of fact, though Texas fever is 
unquestionably more prevalent in places where the conditions are favourable to 
tick life, it has at times been communicated by ticks in all classes of country, 
-and if the germs are picked up in external Nature they must be very widely 
distributed indeed. Moreover, if the contamination is acquired in this vay, 
rather than by transmission from antecedent disease, it has to be explained how 
if comes about that the first few crops or generations of ticks very frequently 
fail to produce any fever. Why do they not pick up the infection, if it exists 
in external Nature, just as readily as later crops? Why is it, too, that ticks 
which have matured for many generations on a herd before any Texas fever 
has appeared, remain, after the disease has eventually swept through it, sure fever- 
producers ? Some experiments have been instituted in the hope of determining 
these matters. 
It has also to be ascertained if any other blood-sucking insects, such as 
some kinds of flies and mosquitoes, are capable of performing the same réle of 
transmitting agent as the tick. In Australia, so far as I am aware, we have 
no evidence of any such thing; on the contrary, we have distinct evidence 
against it. But, on the other hand, a disease apparently identical with Texas 
fever has been observed in various countries where the presence of the cattle 
tick is problematical; so that the possibility of the disease being transmitted 
by some such vicarious agencies must, I think, be admitted, though it is to us 
a matter of small practical importance. 
THE BULLOCK AND THE FEVER. 
The bullock’s part is quite a passive one. He is assaulted bythe tick, 
infected by the microparasite, and tormented by the fever. Probably individual 
animals differ somewhat in natural susceptibility to these things, and perhaps 
various breeds of animals differ also, just as individuals and races of men differ 
in natural susceptibility to any given disease or noxious influence.- But I am 
not aware that constitution, breed, colour, or any such circumstance has been 
proved to have any special protective influence; or that there is any special 
protective virtue in one class of country over another, except in so far as it may 
be unfavourable or otherwise to the life of the tick or of the microparasite. ‘he 
cattle from all kinds of country are attacked alike when removed to places 
where the ticks are known to be fever-carriers. As in the case of many of the 
ills which human flesh is heir to, immunity to Texas fever is most safely and 
satisfactorily attained in early life, when tissue change is active, and vital 
energy and recuperative power are in the ascendant. 
THE FEVER. 
The fever—which is the most important element in the whole drama— 
results from the opposing activities of the microparasite and bullock, and is 
the expression of a deadly combat between the two. The microparasite is the 
attacking party. Having got into the blood, it invades and destroys tlhe blood 
corpuscles, and causes a blockage of many of the minutest bloodvessels or 
capillaries. Perhaps, by such action, it causes a certain amount of irritation 
to the apparatus in the brain which regulates the generation and liberation of 
animal heat, and so causes high temperature. But I think more probably, 
and possibly in addition, it generates a poison in the blood—just as the yeast 
plant produces alcohol in a fermentable liquid—and that the high temperature 
or “fever” is due to an effort on the part of the bullock’s organism to pro- 
duce an antidote or counteracting substance. If it succeeds in this, it over- 
comes the microparasite, and holds it in perpetual subjection, and also any 
future-parasites that may be introduced; and in this way becomes immune to 
their attacks. But, though it thus becomes master of the situation, it does 
not seem to be able to actually exterminate the invaders ; they still linger m 
