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63
semi-detached with ample gardens, and it appeared that the reason
for the inability to control the situation was the fact that the
population had largely lost its immunity. (This has been borne
out in 1930 at the diphtheria immunisation clinic where every
case has been Schick tested. The proportion of immunes has been
found to be only 16 per cent.)
All contacts were swabbed, both nose and throat, and the same
process had been carried out in school investigations.
This, as may be realised, gave an enormous amount of work
to the department, as will be seen by the fact that the total number
of swabs examined during the year was 6021, and this, as would
be expected, resulted in the finding of a considerable number of
positive nasal cases. Doubts of course arise on these occasions as
to whether the bacterial cases which are being picked up are
sources of danger—in other words whether they are virulent or not.
In order to see how things were going, random samples of
cases were sent for virulency tests. Dr. O'Brien, the director of
the Wellcome Research Laboratories, kindly undertook to do this
work for me, so that there can be no doubt as to the accuracy of
the results.
A series of cases were sent, the first of which we regarded as
doubtful as being a true Kleb-Leoffler's Bacillus.
The virulency reports were, with the exception of this first one
which was returned as non-virulent, virulent in every case.
On the face of that, and what one took to be the unsalted condition
of the population, despite what some other Authorities say,
there appeared to be no alternative but to pursue the same course
and to pursue it diligently.
The bacteriological conditions were peculiar during a portion of
the year, in that the confirmatory Neisser staining was extremely
poor. There appeared to be no doubt whatever about the character
of the organism stained with the usual stains, either Loelfler,