1 Srpr., 1901.] QUEENSLAND AGRICULTURAL JOURNAL. 343 
All the prophylactic measures which I have enumerated present, then, 
some serious inconveniences. Now, let us see if we should not have a better 
chance of succeeding by putting the ticks on one side and attacking the 
Piroplasma directly. 
2.--MEASURES APPLICABLE AGAINST THE PIROPLASMA 
BIGEMINUM.—IMMUNITY.—VACCINATION. 
First, Smith and Kilborne, in the United States, then Frank Tidwell, in 
Australia, R. Koch, in Eastern German South Africa, and, lastly, Nicolle and 
Adil-Bey, at Constantinople, have described the particular form of resistance 
that animals attacked for the first time by the disease oppose to a renewed 
infection. 
But what is the importance of this immunity ? Is it sufficiently complete 
and sufficiently lasting to induce one to produce it artificially by the injection of 
some vaccine? When we read what has been accomplished in the United 
States and in Australia, we must be convinced that a first attack confers a 
certain immunity. Still, the percentage of animals which have had a second 
attack is rather high. 
R. Koch is very positive, but his experiments have been too restricted in 
number to carry entire conviction ; besides, one of his animals died on a trial 
inoculation. 
Nicolle and Adil-Bey, whilst admitting the indefinite immunity of 
indigenous animals to the malarial virus, have not had the opportunity of 
experimenting on exported cattle, 7.e., on the most sensitive. We shall see 
that they pin their faith more to a power of endurance than to a true immunity. 
Since the most perfect possible knowledge of immunity should be the 
touchstone of a preventive inoculation, I had to obtain light on its existence, 
its power, its duration, and its mechanism. I have made, with this object, 
nearly 200 experiments, of which I am about to give the results, and especially 
my conclusions. 
(a.)—Natural immunity of animals in the infected zones. 
There is a considerable difference in the degree of immunity, according to 
whether the cattle come from zones slightly infested, very much infested, or 
free from infestation. 
Thus, in the province of Santa Fé, stretching extensively from north to 
south, we see, with very rare exceptions, animals born in the northern parts 
resisting the most virulent inoculations without appearing to suffer the least in 
the world. Animals of the extreme south, on the contrary, are certain to take 
the disease ; and, lastly, in the intermediate zones we find a more considerable 
number of animals which, whilst bearing the infection, have fever and hsema- 
tozoa in the blood for many days in succession. Natural immunity then, 
acquired, be itin youth by the punctures of the ticks, or the result of a first 
infection, or perhaps due somewhat to heredity,* appears to us in various degrees. 
Sometimes the inoculations of very virulent products do not succeed in over- 
coming it; sometimes, on the contrary, one succeeds in inducing a mild 
affection. 
(b.\—Immunity of animals experimentally inoculated. 
All my experiments have been made on animals sensitive to malaria, and 
coming from immune districts.. The virulent form, 7.¢., that ‘which produces 
hemoglobinurea, is followed by an immunity such that in no case, whatever 
may be the quantity, the quality of the virus and the means of inoculation, or the 
virulent injection, was the experiment followed by any result, nor did it cause 
the Piroplasma to re-appear in the blood. 
j *T have had occasion to inoculate a calf eight months old, born of a mother which had the 
virulent disease and reared at my laboratory, and consequently beyond all cause of infection. 
It took the disease consequent upon an injection of 10 ¢.c. of bio into the jugular, and was 
cured after eight days. ‘This experiment seems to prove the insufficiency of the hereditary 
immunity theory. 
