202

Report on Kála-ázar.

must be frequently passing through the human system in order
to keep up their intensity, otherwise they will revert to the
ordinary type, just as artificially intensified bacteria require
every now and then to be repassed through susceptible animals
if their power is to be maintained at a very high pitch for long
periods. Whether these are the correct explanations of the
facts recorded relating to the spread of the disease, is of much
less practical importance than the knowledge of the facts
themselves, for they at least may be safely relied on in consi-
dering the measures which are necessary to check the spread of
the epidemic, and it is for this reason that all controversial
matters have been treated of in this section separately from
the previously recorded facts which require to be explained.