450 QUEENSLAND AGRICULTURAL JOURNAL. [1 Duc., 1898. 
Tick poverty almost invariably affects cattle when they first become 
grossly infested, quite irrespective of whether they have been rendered, by 
inoculation, immune to Texas fever, or are still susceptible to that disease. 
In other words, they may acquire the comparative immunity to the local effects 
of ticks which comes of usage, or become “tick proof,” without being 
necessarily immune to Texas fever; and likewise they may be rendered immune 
to Texas fever (as by inoculation) without being rendered proof against tick 
poverty. These two things are quite distinct. And,as might be expected, 
dips are of unquestionable value in combating the poverty from gross 
infestment, though they are, as far as my experience goes, quite ineffective in 
protecting cattle from the fever. 
THE MICROPARASITE OF TEXAS FEVER. 
So much then for the part played by the tick itself. We have now to 
consider the microparasite of Texas fever, and more particularly its relation to 
the bullock on the one hand and to the tick on the other. 
Its relation to the bullock is very evident, for it,behaves in all respects as 
a true blood parasite. It.multiplies with amazing rapidity when it first gains 
access to the blood of a susceptible beast, invading and destroying a large 
number of the red-blood corpuscles, and thus produces the phenomenon of red- 
water which is so frequently seen in the acute form of Texas fever; and even 
after the complete recovery of the animal, it still persists for an indefinite 
time as a quiescent and inoffensive inhabitant of its blood. : 
The blood ofthe bullock is therefore the natural home of the microparasite. 
Here it flourishes, multiplies, and dwells, and, if the bullock were immortal, it 
might perhaps remain for ever through indefinite generations in this Elysian 
abode. But bullocks are “not built that way,” and some provision has to be 
made for the perpetuation of the microparasite’s race if it is not to be wholly 
extinguished on the death of its host. If it is to continue as a spécies, it must 
obviously ,have some means of effecting its escape from the blood of any 
particular. bullock, and also of gaining access to afresh host. ‘This process of 
transference can be done artificially for it by means of an inoculating syringe, 
and the parasite passed on from bullock to bullock through an indefinite series. 
And from. this circumstance it would seem that all that is necessary for the 
perpetuation of its race under natural conditions is some agent which shall 
perform for it this same office of transmission from one bovine animal to 
another. 
THE MICROPARASITE AND THE TICK. " 
The relations existing between the microparasite to the tick are, I think, 
probably such as to fulfil this requirement. ‘The tick, in fact, appears to act asa 
carrying agent on behalf of the microparasite. But it does its business in 
what seems a rather roundabout and tedious fashion. or, having withdrawn 
or taken delivery of the microparasite with the blood with which it has gorged 
itself, it devotes the remainder of its existence to its own private concerns, 
and leaves the final execution of its duty as a carrying agent—viz., the delivery 
of the microparasite to a fresh host—to the care of its progeny. And this office, 
as we know, they in many instances fulfil with painful precision. 
In some cases, however, I venture to think there is a dereliction of duty 
on the part of the tick, and the microparasite is not transmitted; and then no 
Texas fever is produced by the young ticks. In what department of its carry- 
ing arrangements—with which, indeed, we are quite unacquainted—this occurs, 
Ido not pretend to say. Possibly the tick on the infected beast fails, in some 
cases, to: take delivery of the parasite, or, having done so, fails to hand it on 
to her progeny ; or possibly the young ticks in their peripatetic energy and 
desire to see lite—especially bovine life—somehow lose the run of their 
charge. Or, again, the fault may lie wholly with the microparasite itself; it 
may not have been ina fit state to start on a colonising expedition when it 
was withdrawn by the tick: it may have been too old or too young or other- 
wise incapable. Or, having safely embarked in the tick, it may have been 
