1 Nov., 1897.] QUEENSLAND AGRICULTURAL JOURNAL, 409 
that the otherwise simple and obvious explanation—that some cattle ticks are 
non-pathogenic—should be accepted with considerable reserve. We know, too, 
as has also been already mentioned, that such cattle as we are considering are 
still susceptible to fatal attacks of tick fever, and that immunity in them, as in 
the case of other susceptible cattle (that have never been tick infested), is, In 
Nature, apparently only attained as the result of more or less acute disease— 
that is to say, fever, or as in this case it might more properly be called 
reaction, precedes immunity. 
Touching the nature ot this fever or reaction: It is an old saying that “it 
takes two to make a quarrel,” and the same thing may be very well said of a 
reaction, which is, essentially, a quarrel between some inimical influence, such, 
for instanee, as invading micro-organisms, on the one hand, and the opposing 
forces of the animal attacked on the other. In the case of the aphorism one 
of the parties may be long-suffering, and fail to react even to considerable and 
Jong-continued provocation, particularly if that provocation has been of gradual 
incidence; the time, however, at length arrives when reaction is inevitable— 
either on account of the unbearable increase of the provocation, or through 
some casual circumstance, such as fatigue, hunger, thirst, or excitement, on the 
part of the long-suffering individual, which determines that explosive social reac- 
tion called, in everyday life, a quarrel. After which, asa rule, for a season—often 
directly proportionate to the severity of the disturbance—there is peace. in 
the case of an animal exposed to tick infection, it seems at any rate conceivable 
that an analogous long-suffering characterises the bovine constitution ; it does 
not readily react to the irritation of the ticks, or rather to the microparasites 
which they carry, particularly when the irritation has commenced gradually. 
Tt has been said that a certain amount of reaction—as shown by fever—is the 
general result of a first invasion by ticks, And when a considerable number 
of ticks gain access to a beast simultaneously, as in experimental observations, 
or at nearly the same time, as when a clean beast is put into an infested 
paddock, no doubt this is the result. But the infection of a beast on its own 
run is, in all probability, in most instances, a much more gradual process than 
is generally believed. The first insidious beginnings of tick infestment can 
rarely be known; and in one instance, at any rate, communicated to the writer 
on excellent authority, a herd of 800 dairy cows was under constant observa- 
tion, being milked twice daily, during the three months that ticks were known 
to be advancing upon them, and yet in no respect could there be detected 
amongst these cattle the slightest indication of febrile disturbance. However 
these things may be—and they are here only referred to to indicate the nature 
of some of the mysteries which still surround the subject, or rather of some 
of the problems which still remain to be solved in connection with it—the 
evidence so far to hand would seem clearly to indicate that reaction plays a 
large and, perhaps, essential part in the establishment of immunity when 
brought about in Nature. In any case, the only immunity we know of under 
natural conditions is that which is brought about as the result of more or less 
acute disease. 
How stands the matter in the case of inoculation with “recovered 
blood”? Is reaction here also essential to success? From what has been 
already stated as to the considerations which induced the writer .to suggest the 
plood of a recovered animal for inoculating purposes, it will have been under- 
stood that the fundamental principle of the idea was to bring about a mild attack 
of fever which should protect from a subsequent virulent attack. The mild 
initial attack was regarded as the necessary antecedent of subsequent 
immunity. Actual experience of inoculation by this method, however, has 
“not, invariably, confirmed these anticipations. Tn some instances, as in the 
experiments already referred to at Mundoolun and Glendower, and in a larger 
and more recent one at Mount Pleasant,* a distinet febrile reaction has ° 
* More than 2,000 head of cattle have already been inoculated at this station alone. 
