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rehousing in municipal estates but it cannot be forgotten that information as to new
cases of overcrowding is not likely, without periodic surveys, to be accurate and the
true position is possibly not so good as these figures indicate.
Ample evidence of other valuable work carried out by the Sanitary Section during
the year will be found in those sections dealing with sanitary administration,
supervision of the food supplies, and control of the infectious diseases. A very
high standard has been maintained throughout.
In recent years all over this country much thought has been given to the problem
of the eradication of the bed bug from houses and particularly from those owned by
the municipalities. The problem is much more difficult than it would appear at
first sight. The bed bug is small, it shuns the light and takes advantage of every
cavity which will give it shelter. Under suitable conditions it multiplies rapidly
and it can live for a long time without food. For these reasons it is a very difficult
insect to abolish. There are many insecticides—proprietary and otherwise—on the
market; the continued presence of the bed bug and the very multiplicity of these
remedies indicates how useless most of them are. The bed bug frequently invades
new houses, being in most instances transported there in the furniture. It is easy
to kill it in transit by the use of a suitable fumigant in the furniture van—hydrogen
cyanide, one hundred per cent. effective, is most often used. In homes however,
this cannot always be selected—it is too dangerous a chemical, for example, in a single
dwelling in a block of flats. Because of this, efforts have been made to discover a
fumigant which is toxic to the bed bug, and is not harmful to man. One such is
washed heavy coal tar naphtha. In Woolwich in the last eighteen months we have
been doing research work in connection with its use. The story of the experiments
and of the difficulties overcome, is set out in Section IV. In washed heavy naphtha
we appear to have a disinfestant which is easily applied, which is non-toxic to man,
which does not damage paint, which has no dangerous carry over and which is successful,
provided the atmospheric conditions are right—a temperature of 60°F. is
necessary. The process is not yet perfected but this should not require much more
research. Naphthas vary in constitution, some containing a greater proportion of
elements toxic to the bed-bug than others and the one we have been using is now
being fortified in this respect. It can safely be said that in naphtha we have a
disinfestant which solves, safely, effectively and cheaply, the problem of the
disinfestation of the flat or tenement house, a situation in which hydrogen cyanide
in this country at least can never be used.
As regards the infectious diseases there was a decrease of scarlet fever (428
compared with 609) and an increase of diphtheria (297 compared with 176). There
were no deaths from scarlet fever and ten from diphtheria. Diarrhoeal diseases
shewed a marked increase—81 cases of dysentery of a mild type and 65 of epidemic
diarrhoea being notified. Measles was not present in epidemic form. The number of