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equally activc as immunisers. The ordinary healthy
carrier—namely, the immune person who has just been
exposed to infection and temporarily retains the infecting
organisms—will probably, as compared with the chronic
convalescent carrier, play amuch smaller part in causing
actual cases of illness but is equally effective in handing
out immunising doses.
2. The age distribution of the population on the Estate
was discussed in detail in the Annual Report tor the ..
year 1927.
3 and 4. Graphs 2 andi 3 in the 1928 Report showed that
the greatest incidence of infection occurred 'in the
period averaging 6 to 18 months residence on the
Estate; Further, table '5, which gave the incidence
of infection for both diseases on each section of the
Estate, showed that there was a lag period of months
in almost all instances before any particular section
succumbed to infection, and that, in general, infection
when it occurred, has been heavier in those sections
which developed rapidly. Also the varying nature of
the three pairs of graphs showing the periods of incidence
before infection for each of the three years supports
this suggestion. Up to 1926 development was
relatively slow and no effect was apparent. By 1927
the period had just been reached when the effect of the
more rapid development of 1925 made itself felt. This
was much more marked for the year 1928, This year
was the peak year of expansion and is reflected by
the marked peak showing incidence amongst residents
of about 6 months' duration. The slower development
of 1929 gave a flatter curve with a maximum incidence
after 12 to 18 months' residence.
With regard to the importation of infection from London,
it was shown in the report for 1923 that there was a
heavy incidence of infection within the first few weeks
residence here and that in a number of cases, definite
association with a London case was shown. Apart
from the possible risk of infection to susceptible
both at the places visited and in congested carnages
in transit to and fro, must be added the possibility of
infertion being brought down to the district by visitors
from the congested Metropolitan areas.