CHAPTER I.
Part IV.—Inoculation.
The experience of plague and measures for its management acquired in Bombay during
the past 3 years has demonstrated that the ordinary means used for " stamping out " the
disease have not met with the success hoped for. The fact is forced upon one that, in a
large town, once the disease has taken root, it will re-appear year after year, and that—so far
as present experience guides us—its virulence will show no sign of diminution, as is the case
with some other epidemic diseases. If the disease then cannot with certainty be " stamped
out," the only other resource left is to try to render the people of the infected town immune
to plague, so that, though living with the cause of the disease all round them, they may remain
free from attack. It is only necessary to refer to the effects of vaccination for small-pox, to
make it clear that it is not impossible to immunise a population, so that, though conditions giving
rise to a disease may exist in nature all around, yet cases of that disease are comparatively rare.
It is a well-known fact that diseases, such as small-pox, typhoid fever, cholera, etc., appear as a
rule only once in the same individual, and a person who has recovered from an attack of one of
these has the comfortable conviction that in all probability he will not suffer again. He or
she has become "immune" to that disease. It has been ascertained that these "zymotic"
diseases as they are called, are each one caused by a special germ of its own. These
germs can be separated from the bodies of persons suffering from such disease, and grown
on suitable media in laboratories. From these germs each disease can be produced,
just as cereal crops can be produced by sowing the seed of the required grain in suitable
soil. Each grain produces its own particular crop and no other, so each different germ
of disease produces its own disease and no other. One important difference, however,
appears, viz., in the case of cereals one can go on, year after year, sowing the same crop in the
same field, and a yield will be produced and a harvest reaped. In the human body, on the
contrary, the seeds of disease having once been sown, and the disease crop matured,
a second crop will not grow. Even if the seeds are sown, they do not germinate, the avail-
able material in the soil has been used up, or the soil has been so altered that no second
disease-crop can be produced; in other words, the individual has become immune. It is
believed that immunity is caused by the reaction of the body to the poison excreted by the
disease-germs as they grow in the body. If, then, we cause the germs to manufacture
their poison in bottles, and, after killing them by heat, inject a measured quantity of this fluid,
the same effect will be produced on the body soil as though the germs had actually lived in
that body and produced their poison there. It was considerations such as these that guided
Haffkino in working out " vaccines " for cholera and plague, and the success or otherwise of
his plague prophylactic may be judged from the statistics now to be given.
As the results of 3 months' labour at the life-history of the plague bacillus, Haffkine was
able to inform the Government of India, in a letter dated 16th January 1897, that he had been
able to prepare an inoculation fluid, which promised, on the analogy of the results obtained pre-
viously by Pasteur in connection with anthrax and rabies, and by himself in the case of cholera,
to produce in the human organism a considerable resistance to plague. The now well-known
effect on human beings he described from its action on himself, as he had been inoculated with
a dose which turned out to be 4 times stronger than that now fixed as the standard. Shortly after-
wards, 77 leading citizens of Bombay were inoculated to demonstrate publicly the complete
harmlessness of the operation. The preparation of the prophylactic is detailed in the British
Medical Journal for June 12th, 1897, and the Indian Medical Gazette for June 1897, and though