1 Sepr., 1901.] QUEENSLAND AGRICULTURAL JOURNAL. 345 
only will they be able to resist natural contamination, but their immunity will 
be found to gain strength. This authentication is all the more fortunate, and 
ought not to be neglected, if successful preventive vaccinations have been made. 
Ts it immunity or only tolerance ? 
According to Nicolle and Adil-Bey, a first inoculation confers tolerance 
rather than immunity. 
These authors base their opinion on the persistence of the Piroplasma in 
the organism, and the constant appearance of the latter, at least amongst adult 
beasts, after a fresh virulent inoculation. 
Smith and Kilborne in the United States, Pound in Australia, have 
declared the persistence of the hematozoa of bovine malaria in the organism. 
On the other hand, many observers have described the frequency of the 
Piroplasma in the blood of great ruminants attacked by bovine plague, and 
quite recently Nicolle and Adil-Bey have shown, by conclusive evidence, the 
singularly favourable influence of the microbe of bovine plague on the 
Piroplasma. Here is one of their experiments :-— 
A Crimean animal, aged 14 years, was inoculated on 27th March, 1898, 
in the veins, with ~5 ¢.c. of malarial blood. It exhibited fever and hematozoa. 
It was again inoculated, sub-cutaneously, on 380th June, 1898, with half a cubic 
centimetre of pure plague virus. It contracted bovine plague, but showed at 
the same time hematozoa both during life and after death. In the interval 
between the two injections the animal’s health was-perfectly good. 
This phenomenon of the persistence of hematozoa in the organism was 
too important for me to neglect its study in my turn. 
I confined myself at first to examining for some length of time the blood, 
which was the more easy for me to do as I had already undertaken the task of 
daily counting the red corpuscles. 
Under these conditions I examined every day, and for several months, the 
blood of animals affected with bovine malaria, so that I have been able to prove 
that in the virulent form, the rapid disappearance of hematozoa towards the 
eighth or tenth day is only apparent, for, at long intervals, only very few 
infected blood corpuscles are seen. 
Some examples :— 
a. A bull inoculated on the 29th April, 1899, began to show a few hematozoa 
on 7th May. During the following days, until 15th May exclusive, they were very 
easily found, then they seemed to disappear, when, on the 24th May, I again found an 
infected corpuscle. On the following days the most minute examination failed to 
- show any, except that on 10th June I found acorpuscle containing a hematozoic type. 
The examinations, although continued to the 1st July, disclosed nothing in the corpuscles. 
On the 15th May this animal had entered the stage of thorough convalescence. 
6. On the 21st June, 1899, a bullock received a sub-cutaneous injection of 10 c.c. 
of virulent blood. From the 22nd to the 2nd July I found hematozoa present. Again, 
on the 26th July and 12th August, I met with an infected corpuscle. I had found 
nothing during the interval, and my examination lasted till 1st September. 
c. [ may also cite the case of the beast which relapsed, in which I found 
hematozoa from the first day of inoculation to the 10th exclusive. I found them 
again on the 28th June, and on the 7th and 30th July. In the interval, and up to 
4th August, I found no micro-organism in the blood. 
Many a time, in examining the blood of animals which had been diseased, 
T haye found a corpuscle infected by the Piroplasma type three months and 
even four after inoculation. And further, the intra-venous injection of a 
healthy animal of 20 ¢.c. of blood taken from an animal cured several months 
previously, has occasionally caused the malaria. These facts prove that after 
the Piroplasma bigeminum has shown itself in greater or less abundance during 
ten days, it seems to disappear, but that in reality it re-appears at rare intervals 
for a long period. 
__ Smith and Kilborne have also proved the re-appearance of the Piroplasma 
without fresh inoculation; they even go so far as to affirm that about a month 
r the sickness, there is always a relapse, a statement which is a little 
exaggerated. 
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