350. QUEENSLAND AGRICULTURAL JOURNAL. [1 Szpr., 1901. 
small number of infected corpuscles, the absence of general phenomena and 
acquired immunity which presage a possible extra-corpuscular evolution of the 
Piroplasma. 
This last point appears new to me, and to be also of the greatest 
importance. 
Since immunity can renew itself as we have just seen, its duration should 
‘ therefore be unlimited. Yet experiment proves the contrary to be the case. 
Whatever may be the importance of the latent parasitism, the organism 
constantly seeks to get rid of it in the same way as it tries to avoid the 
retention of the poisons. 
Hence it is evident that this affranchisement will be all the more easy and 
speedy according as the microbian or toxic retention is of least importance. 
If the natural immunity observed in permanently affected centres, and 
which begins with the calf, appears illimitable, it is because this immunity is 
incessantly renewed by the punctures of the ticks. 
The first inoculation, or even the several primary inoculations, are too mild 
to leave in the organism a sufficient quantity of spores capable of preserving 
immunity for a length of time. The proof of this lies in the fact that young 
cattle born in the infected districts, but withdrawn after two or three months 
to be raised in the lucerne fields, protected from inoculation, contract bovine 
malaria when they are taken to contaminated places. ; 
In the same way, the receptivity of cattle which would only have had 
slight attacks and would remain some time without receiving any more, would 
reappear, especially if they were suddenly exposed to a severe inoculation by 
ticks. i 
Under natural conditions we see, from time to time, epidemics breaking out ~ 
in infected zones amongst native animals. These epidemics arise perhaps from 
no other cause. 
To sum up, the long duration of the refractory state in bovine malaria is 
the consequence of successive immunities determined by repeated infections 
checked or abortive, either endogenous (latent parasitism) or exogenous 
(punctures frequently renewed by ticks). I do not think I am too bold in think- 
ing that the facts revealed by the study of the refractory state in bovine malaria 
will throw light on many hitherto obscure points concerning immunity in 
certain parasitical or microbian diseases. 
Although the retention of microbes or poisons in the organism is one of the 
most variable phenomena in its duration and in its effects, according to the 
nature itself of parasites and poisons, it must be admitted that this retention 
may prove to be an important factor in the production and in the persistence of 
immunity. 
PREVENTIVE INOCULATIONS. 
Since a first attack, even a light one, confers immunity, itis natural to seek 
to artificially produce this immunity by means of preventive inoculation. 
Nicolle and Adil-Bey had already pointed out, that the serum of animals 
which had recovered and of hyper-vaccinated animals, is neither curative nor 
preventive. 
It has, however, appeared to me that in inoculating a healthy animal sub- 
cutaneously with 100 to 200 ¢.c. of the hemo-globinemic serum of a diseased 
beast, and in repeating this inoculation for two or three days in succession, I 
have obtained a very slight resistance compared with that of the controls, but 
so feeble at times that I cannot affirm the immunising property of this serum.t+ 
* T again refer, en passant, to the importance of the quantity and quality of the ticks from 
the natural infection point of view. umerous experiments made with ixodes of different 
productions prove this view. 
+The serum was kept forty-eight hours inthe warm chamber to make sure of its inocuousness: 
It will be remembered that after forty-eight hours in the warm chamber, blood loses all virulence. 
Perhaps the hemo-globinemic serum is more or less rich in hematozoic poison, and contains at 
times a rather large quantity of it, so as to give the inoculated animals a slight resistant power. 
