1 Mar., 1898.] QUEENSLAND AGRICULLURAL JOURNAL. 217 
Again, in the all-important matter of acquired immunity, we know that old 
residents of malarious places are less liable than new-comers to fall victims to 
the malignant forms of malarial fever, but that nevertheless the protection 
conferred by one attack of fever is but slight and evanescent.* In the case 
of the bovine disease, on the other hand, there is some good evidence to show 
that a very considerable protectiont—if not absolute immunity—follows an 
attack of the acute fever. 
METHODS OF COMMUNICATION. 
A certain rough parallelism has been seen to exist in the life histories of 
the tick fever and malarial organisms; also some striking resemblances in the 
clinical and pathological aspects in the diseases they respectively produce. 
There would appear to be some equally striking analogies in the means by 
which each disease is spread or communicated. 
The Cattle Tick and Tick Fever.—\t has been already stated that the 
cattle tick is the agent by which tick or Texas fever is communicated. This 
fact has been definitely established by a number of carefully conducted experi- 
ments carried on both in America and Queensland.§ It has been proved and 
re-proved ; it has been tested and re-tested ; and always again and again con- 
firmed; so that there is no room for doubt in the matter. The experimental 
evidence, to anyone who will be at the pains to examine it, is perfectly 
conclusive. || 
The micro-organism evidently lives and multiplies as a true parasite in the 
blood of the bullock. Its precise relation to the tick is not so clear; nor for 
our present purpose need it be discussed. All we are concerned, in the present 
connection, to know is that the tick is the means by which the micro-organism 
finds its way into the bullock, and -is probably also the means by which—in 
some as yet unknown shape or form—it eventually gets out again. 
The Mosquito and Malarial Disease.—The researches of Dr. Patrick 
Manson and Surgeon-Major Ronald Ross seem to indicate very strongly that 
the mosquito is the agent by which the liberation of the malarial Plasmodium 
from its human host is effected; also, that this insect is very closely associated 
with the life history of the Plasmodium outside the human body, and is 
probably the means by which the malarial germs are disseminated in external 
nature, and become widely distributed in earth, water, and air, and is thus, 
indirectly, the means by which the disease is spread.** 
Following as a commentary on the publication of Dr. Manson’s views, 
there appeared a long and:interesting article by Dr. Amico Bignami.t+ This 
eminent authority inclines rather to the view that the malarial organism is 
* This fact has been explained on the supposition that such antitoxins as are produced in the 
human body in response to the malarial toxins (?) are quickly eliminated. ‘‘ Acquired Immunity,” 
by Dr. G. Archibald Reid. Lancet, 11th September, 1897. : 
+ Inoculation for Tick Fever: Its Prospects and Problems. Queenslund Agricultural 
Journal, Nov., 1897. 
No instance of a second attack produced by the injection of virulent blood has, so far, 
been recorded. Many such injections have been made by the writer into recovered cattle without 
obvious result. f : 
§ Highth and Ninth Reports of Bureau of Animal Industry, U.S. Dept. of Agriculture. 
Thirty-seventh Bulletin of Missouri Experiment Station. Report on Tick Fever by Queensland 
Commissioners, 1896. Queensland periodical literature, passim. ° 
|| It is necessary to emphasise this fact because there are those, both in Queensland and 
America, who deny it. These persons are not always the most reticent in the community, and 
are unfortunately, as a rule, little influenced in their judgments by experimental evidence—or, 
indeed, by evidence of any kind. Even the striking object lesson of ticks and disease marching 
hand in hand into Queensland is lost upon them. 
| Manson, speaking of the malarial organism (Goulstonian Lecture, No. I., 1896), says: ‘‘The 
individual Plasmodium gets into man designedly, and, this being so, we may be quite sure that 
just as provision is made in its economy for a passage into the human body, so provision is made 
in its economy for a passage out of the human body. Such a provision is absolutely necessary 
for all true parasites ; otherwise, were this not the case, the extinction of the parasite, not merely 
as an individual, but as a species, would be inevitable on the occurrence of the death of the 
host.” Precisely the same argument, of course, applies to the organism of tick fever. 
** Goulstonian Lecture, No. II. Zancet, 2ist March, 1896. 
+t Hypotheses as to the Life History of the Malarial Parasite outside the Human Body. By 
Dr. Amico Bignami. (Translated from the Italian by Dr. Sandison Brock, of Rome.) Zancet, 
14th and 21st November, 1896, 7 ' 
