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4. The Commission continued to work up to 1913 and their studies have
formed the basis for our exact knowledge of the epidemiology of bubonic
plague. The particular organisation adopted proved a most effective one
and the Commission is regarded as a model for such investigations.
5. The association of rat and human plague had been recognised even
from biblical times but the dependence of human outbreaks on rat epizoo-
tics and the exact relationship between the two had not been determined.
Gautier and Raybaud and in India, Hankin, had suggested the possibility
of insect transmission from rat to man but it was not until the Plague Re-
search Commission was formed that this was proved and the factors con-
cerned demonstrated. The credit for proving the flea transmission of
plague must be largely attributed to Liston. The detailed studies of the
Commission have shown the essential facts on which plague preventive
measures can be based. The voluminous reports of the Commission in the
Journal of Hygiene from 1906 to 1917 provide a wealth of information on
every aspect of the disease.
6. In subsequent work carried out by different observers the existence
of a flea-species factor influencing the epidemiology of the disease in
different areas was shown. Along with the work on the methods of trans-
mission of plague, and in fact preceding it, was that of Haffkine on a
prophylactic vaccine. This was one of the first vaccine to be used on it
very large scale for the prophylaxis of a human disease. An account of the
vaccine and its development has been recorded in Indian Medical Research
Memoir No. 27. This vaccine with certain modifications is still in use in
India and is relied upon as a major preventive measure.
7. Recent research on plague.—Plague research has continued since the
disease was first introduced to India, the main centre of work being the
Haffkine Institute, at which laboratory investigations have been carried
out and from which field investigations have been instituted. Other field
investigations have also been instituted in different parts of India.
8. Researches at the Haffkine Institute.—The work at the Haffkine
Institute which is in progress consists of (a) further studies on plague
vaccine with a view to its improvement, (b) the preparation of a therapeutic.
serum and (c) studies in relation to epidemiology.
(a) Anti-plague vaccine.—More exact methods of determining the value
of the prophylactic vaccine and the comparative value of different types
of vaccines have been worked out and these methods have been applied to
the study of the influence of different factors on the efficacy of the vaccine.
By the methods of test used, it has been indicated that a marked improve-
ment in the vaccine is obtainable and the method of manufacture has been
revised in accordance with the observations made. Work on the subject is
still continuing. Comparisons have been made between the Haffkine
vaccine and other vaccines and it is claimed that the Haffkine vaccine as
now revised is superior to other types.
(b) Anti-plague serum.—This subject has been under study since 1925.
Sera have been raised in different animals and their value tested in experi-
mental animals. Trials have been carried out as to the value of the sera