1 Sepr., 1901.] QUEENSLAND AGRICULTURAL JOURNAL. 349 
The organism, however, exerts all its powers and means of defence to 
oppose the advance of the invading hematozoa. 
All the red corpuscles are not equally sensitive to the action of the 
hematozoic poison. At first a few, afterwards a great number, are slowly 
impregnated by it and gradually accustom themselves to it. 
Becoming so accustomed, their power of resistance increases, and they 
become unadapted to harbour the spore of the parasite destined to develop into 
the piriform state. 
As the number of these resistant corpuscles increases, the diseese declines ; 
the organism triumphs over the micro-organism, and the cure begins. 
The action of the toluylene-diamine on the blood corpuscles furnishes a 
yery instructive example of this conformability of the red corpuscles. 
Injected sub-cutaneously, the toluylene-diamine rapidly changes the red 
corpuscles, and may determine the hemoglobinemia or even the hemoglobinurea. 
but it produces scarcely any effect when an animal has been accustomed to 
doses of this poison—weak at first, and then gradually increasing.* 
Henceforth, as they can only find corpuscles accustomed to the poison, the 
hematozoa cease to multiply in the piriform character. The cycle of evolution 
stops short at the stage of sporulation. 
But it must not be concluded that, because the parasite is no longer seen 
in its characteristic pear shape, it has been completely eliminated. 
In this lies the main point. The specific parasite of bovine malaria, the 
Piroplasma bigeminum does not entirely disappear from the organism.  T¢ 
remains in the form of a spore, changing, slowly perhaps, into the round form to 
again become the spore. 
We have seen the spores developing into the round form in the changed 
blood of diseased animals, placed in the warm chamber. It is not at all 
impossible that the same thing may take place in the organism under certain 
favourable conditions. It is these same spores which, circulating in the 
organism of animals long since recovered, may be taken in by the ticks at the 
same time as the blood, and be afterwards transmitted to healthy animals. A. 
long time after recovery, at long intervals,.and without the animal undergoing 
further inoculations, natural or experimental, the parasite re-appears in the 
characteristic endo-globular pear-shape. 
The supposition that immunity is not antagonistic to persistence in the 
organism of the specific microbe in the latent state. 
We find in bovine malaria a striking proof of this. 
A. first attack confers lasting durable immunity. Eight months after 
recovery, injections of enormous doses of malarial virus have no effect. 
And more than this: This latent parasitism, which creates immunity, will 
also contribute to ensure its long duration. 
As a matter of fact, the poison secreted by the parasite during the whole 
course of the disease, is not quickly eliminated. 
So long as it remains in the blood, it produces, by mithridatisation, 
(applying an antidote) globular resistance and the refractory state towards the 
wroplasma. 
But there comes a time when it is completely eliminated, or is merely in 
insufficient quantity in the tissues. Then, some fresh red corpuscles which 
have not been accustomed to the poison become infected by the spores. It is at 
this moment that the endo-globular Piroplasma once more makes its 
appearance. 
By means of this fresh infection, almost always mild in form, the organism 
renews its immunity. So that in bovine malaria, the refractory state is, in 
reality, the consequence of successive immunities. Its persistence is thus 
explained. 
The experiment proves that a very small number of infected corpuscles is 
sufficient to enable the organism to recover immunity. It is precisely this 
* See the very interesting thesis of Dr. A. Vast+ Paris, 1899. 
