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110
Report of the Medical Officer of Health.
Other factors also, as mentioned in my Report for 1912, have
contributed to this decrease, notably the diminution in the amount
of horse manure, and the tar spraying of the principal roads in the
Borough.
There is, however, one measure which deserves the serious
consideration of the Council, viz., the more frequent removal of
house refuse. There are doubtless serious, but not unsurmountable
difficulties in the way, but these might be in time surmounted and
a universal daily removal substituted for the present system.
With regard to the relation between house refuse and the
prevalence of house flies, some interesting observations and experiments
have been made during the past year at the Dust
Destructor. It was noted that during July, August and September,
the dust carts swarmed with both larvae and pupae of the house fly,
larvae especially being present in enormous numbers. The great
majority of these were naturally destroyed when the refuse was
deposited in the cells of the Destructor, but their presence in the
house refuse in such numbers convinced me that the main cause
of the prevalence of house flies was the storage of house refuse on
premises, and that horse manure, which in country districts is the
favourite breeding ground, is not the cause of their prevalence in
London.
A series of experiments were carried out to ascertain if the
use of any substance, disinfectant or otherwise, would prove of any
value in preventing the development of flies, and it was found that
out of a large number of substances used only three gave satisfactory
results, these three being paraffin, naphthalin, and carbolic
acid.
The following Table shows the material used, the time of exposure
and the result. It is interesting to note that neither Paris
Green, which is largely used in America, nor perchloride of mercury
which is a powerful poison, had any effect on the larvae,