194

Report on Kála-ázar.

furnish a rational foundation for the consideration of preventa-
tive measures.

     To make the matter as clear as possible, I will first state
exactly what I believe to be the nature of the epidemic, and
then discuss the propositions that are involved in this view of
the disease.

     Kála-ázar is, I believe, an epidemic of malarial fever, which
originated in an intensification of the ordinary malarious fever
in the Rungpore district in the early seventies by an extra-
ordinary succession of unhealthy seasons, until it attained to
the powers of infection; and that it has spread for the last
twenty years slowly up the Assam Valley as in a wave of
increased mortality due to this intense communicable type
of malarious fever, having found in the districts which it has
traversed a suitable soil for its propagation.

     This view involves the following propositions: (1) that
malarial fever may, under exceptional circumstances, become
intensified to such a degree as to attain to epidemic proper-
ties; (2) that malarial fever when it has become sufficiently
intensified and is introduced into a suitable soil, may spread in
an epidemic form over considerable areas, and cause an ex-
ceptionally great mortality, in the absence of any changes in
the physical or sanitary condition of the places affected;
and (3) that the germs of the disease must in some way be
able to get out of one person into another, either directly or
indirectly, after passage through the soil, which is obviously
necessitated by the conditions of the second proposition.

     The first of these propositions requiries very little argu-
ment, as the facts given in the last section regarding the
"Bardwan fever," which was of an admittedly malarious nature,
is alone sufficient proof of its truth, while many other instances
in which malaria has become epidemic are on record. It is
also well known that malarious fevers vary very much in their
intensity in different places, and in different years in the
same place. When we talk of an unhealthy year in India,
we usually mean one in which the mortality from malarious