1 Atva., 1901.] QUEENSLAND AGRICULTURAL JOURNAL. 267 
In all my experiments, the period of incubation has averaged from seventeen 
to eighteen days—the shortest time was twelve, and the longest twenty-eight 
days. ‘The last period would seem to be quite exceptional. This period of true 
incubation must not be confounded with the time which may elapse between 
the arrival of the cattle in an infested zone and the appearance of the disease, 
pecnuse these animals may remain for a longer or shorter time free from 
ticks. 
STUDY OF THE PARTICULAR FUNCTION OF THE TICK IN THE 
TRANSMISSION OF BOVINE MALARIA. 
We must now ask ourselves, What is the particular mechanism employed 
in the transmission of bovine malaria by the ticks ? 
Here is the problem: Ticks gorged with infected blood, left on the soil 
or carried to the laboratory, lay eggs which soon hatch out. The young larve, 
which crawl on the earth or under a bell glass, when transplanted on to a 
healthy beast, either by their own movements or by the hand of the experi- 
menter, often induce bovine malaria. How? By what mechanism? My 
researches on the transformation and sporulation of the Péroplasma bigeminum, 
even if they do not furnish a definite solution of the problem, throw a vivid 
light on the particular agency of this propagation. 
After the labours of Smith and Kilborne, of Pound, of R. Koch, and of 
myself, there can no Jonger remain any doubt concerning one main fact—viz., 
the ticks gorged with infected blood give birth to other ticks, which themselves 
are infected also. 
But the infection of these young ticks, is it endogenous, that is to sav, 
does it already exist in the egg which has produced them; or else, is it exogenous, 
that is to say, are these young ticks infected after being hatched from the 
eves? One might well think, indeed, that the entire organism of the tick 
developed on a diseased animal will be infected by the spores of the Piroplasma 
bigeminum ; even its eggs will not have been able to escape the infection by 
these spores, so that the hexapodean larva which is born of them will be equally 
infected, and, hence, will be able to transmit its germs to the animal which 
afterwards harbours it. 
Unfortunately, up to the present, we are not acquainted with any process 
of staining which will enable us to distinguish the spores of Pzroplasma 
bigeminum, amidst the enormous quantity of diverse granulations met with in 
the eges, and in the bodies of the young ticks. 
This hypothesis, which admits the possibility of the passage of the spores 
into the egg, is, however, not indispensable in order to explain the transmission 
of bovine malaria by means of the ticks. 
In fact, when one watches the hatching of the eggs, it is seen that the 
larve do not at once quit the spot where they were hatched out. They remain 
there for a period of from twelve to twenty-four hours, often longer, wandering 
about amongst the eggs not as yet hatched, and amongst the remains of the 
shells. Then they end by dixpersing, most generally trying to climb. 
It is possible, then, that the eggs fouled on the outside by the mother, 
retain on their shell a certain quantity of spores of the Piroplasma which are 
quite capable of infecting the young larve. 
What makes this hypothesis very probable is the fact of the active inter- 
vention of the mother’s rostru « during the hatching process. It is the rostrum 
that casts the eggs outside the oviduct, according as they are hatched. It 
appears to exert a sort of rhythmic pressure on the oviduct, of which it perhaps 
moistens the orifice. - 
In walking, the larva often touches the places over which it walks with its 
rostrum, and particularly with the barbed dart (Plate X., Fig. 2), which is 
admirably adapted for collecting the spores. 
If the surface of the eggs is soiled by the spores the young tick loads its 
rostrum with them, as it would also do in crawling over the ground soiled by 
Le 
eh 
ee 
ee 
i 
Kt 
iis 
if 
{ 
\ 
