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.
Research was then undertaken on much wider basis including epidemiolo--
gical, clinical, pathological, bacteriological studies.
5. The results of treatment work attracted large numbers of cases of
leprosy in the earlier phases, and thus greatly facilitated a clinical study
of the disease. It was found that the milder forms of leprosy of the
"neural" and "neuro-macular" types were very much more common than
had previously been imagined, and it was also found by observation of
such cases over a number of years that in many of them the disease was self-
limiting, the signs of the disease remaining quiescent or inactive for
years or permanently. Most of these cases showed no bacilli and are
therefore considered not to be infectious. It became obvious that text
book descriptions of leprosy as being highly infectious, always progressive
and ultimately fatal were not true of most cases of leprosy in India.
6. These clinical findings were verified by studies of the incidence of
leprosy in various parts of India by means of sample leprosy surveys.
These surveys showed that while leprosy was many times more common
in India than had ever previously been realised, between one half and
two thirds of the cases were of the relatively mild type, and many of them
were of little importance from the public health stand point.
7. These clinical observations carried on systematically over a long
period of years and correlated with pathological and bacteriological findings,
have given us a better insight into the nature of the disease and have
greatly improved our knowledge of diagnosis and prognosis. We are thus
enabled to diagnose the disease at a much earlier stage, to recognise a
number of previously unrecognised manifestations of the disease, and to
form an opinion in many cases of leprosy regarding the seriousness or
otherwise of the infection and regarding the probability of the disease
increasing. We can express an opinion as to whether treatment is likely
to be of value or not and whether a case is infectious or likely to become
infectious.
8. Epidemiological studies have already been mentioned. When first
instituted and for a number of years afterwards the work was chiefly
of an extensive nature, information being collected of the incidence and
the forms of leprosy in large areas in a short time. More recently the
need for intensive work in limited areas has become apparent and this
is now being attempted with the object of studying every factor which may
contribute to the cause and to the spread of leprosy.
9. As one result of the clinical, epidemiological and immunological
work, it has become increasingly clear that immunity to leprosy is com-
monly found in adult life, but in infancy and adolescence immunity is
low and exposure to infection is commonly followed by the development
of the disease often in its severer forms. The problem of the control
of leprosy appears to be very largely the problem of prevention and in-
fection of young children. There are three ways of attempting this. The
first is the removal of the children of infectious parents from their
homes to institutions immediately after birth; the second is the removal
of parents to institutions, and the separation of the parents from each
other, some other provision being made for the children. The third is the