1 Ava., 1901.] QUEENSLAND AGRICULTURAL JOURNAL. 271 
' Collected immediately, these ticks will disclose corpuscles containing round 
or even piriform hematozoa, which one can watch to note the appearance of 
the spores. 
4, An apparently more serious objection is that which arises from this 
very exact fact:—The substance of the ticks or of the eggs injected under the 
skin of sensitive animals is absolutely inocuous. 
Observations and experiments have taught us, in fact, that the passive 
spores are incapable of themselves of infecting the organism by supplying 
Piroplasma ; they require a special favouring cause, probably a venom. ~ 
5. Horses, mules, asses, and sheep in certain districts are covered with ticks 
without tts having been proved that a single case of bovine malaria has occurred’ 
amongst these animals. 
These facts are quite in conformity with the results of experimental 
inoculation; whatever may be the quantity or quality of the virus injected, 
never does sickness attack the horse, mule, ass, or sheep. But a great number 
of ticks may, in sucking their blood, cause in these animals, as they do in the 
case of immune cattle, an emaciation so serious as to entail consumption and 
death. 
6. Ticks which do not pass from a diseased toa healthy animal, cannot 
serve as agents of contamination. 
We know that young ticks already bear the germs of disease the moment 
they infest the cattle. 
Furthermore, my observations have proved that the ticks can transport 
themselves much more easily than has hitherto been believed to be possible. 
The males detach themselves to seek the adult females. As soon as they 
have found one, they puncture the skin with their dart close to her. The females. 
themselves move off when they find themselves ‘in an inconvenient spot.. 
Lastly, the ticks which have not been completely developed, and find them-- 
selves located on a dead beast, are not destined to perish on that account. 
If one watches them for several days, as I have done, the large females: 
will be seen to detach themselves first, then the males, and lastly the smaller 
ones. It is the nymphs and the mature females which remain the longest time 
before moving; some die on the spot, others cast their skin, but the majority 
detach themselves, and seek a new host which may then become infected. | 
It is especially during the night that the Ixodes make the journeys ; this is 
in favour of the ticks. Cattle usually lie down all night—it is the reverse with 
the horse—-so that the ticks have all the leisure needful to spread themselves 
over their hosts. 
OBSERVATIONS AND EXPERIMENTS ON NATURAL 
CONTAMINATION. 
How New Centres of Infection are Created. 
All the observations made in the United States agree in recognising the 
danger to which cattle are exposed when transported from clean districts to 
districts infected by malaria. (The latter correspond with the hottest regions.), 
It is the same in the Argentine Republic, where cattle leaving the south are al) 
the more exposed as they travel more to the north.* (Plate XVI.) 
It has also been observed that all seasons of the year are not equally 
dangerous from a contagious point of view, in connection with malaria. As a 
yery general rule, heat favours contamination, whilst cold reduces it or renders: 
infection difficult. The reason is not hard to discover: It is the warm seasons: 
which favour the development of the ticks, and nothing is better proved than 
the popular saying, “ Tick year, Tristeza year.” Still, it is not the very great: 
heat which is most favourable for the evolution of the tick; the latter prefers. 
a moderate and moist heat, such as occurs at the end of the summer and autumn 
*It must not be forgotten that South America is in the Austral hemisphere, and that, 
consequently, the hottest zones are situated in the north. 
8 
