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area. Curiously enough almost, but not quite, coincidently with the enteric fever epidemic an outbreak
of dysentery occurred in one of the Council's asylums, some 500 or 600 yards to the northwest
of the place of deposit of the house refuse. The outbreak of dysentery was attributed at the time
to the presence of an excessive number of flies in the asylum. Now, consideration seems to make it
clear that whatever value be at first sight attached to explanation by a fly hypothesis of the localised
outbreak of enteric fever, 300 yards to the north-east of the refuse deposit, and to a similar explanation
of the dysentery outbreak, 500 yards to the north-west of the refuse deposit, there must arise some
question as to accepting these two hypotheses in the light of the fact, that during the same hot weeks, the
two outbreaks occurred in areas so differently situated with regard to the source of origin of
the flies. The strict localisation of the enteric fever outbreak, and, in less degree, of the dysentery
outbreak, might perhaps, on a first study of the circumstances of either outbreak, be defended by
reason of the somewhat partial distribution of habitations in the locality, but the ground of
such defence is cut away by the occurrence of the two outbreaks. In order to explain the circumstances
on the fly hypotheses, it becomes, in fact, necessary to imagine that a cloud of flies was
transferred 200 or 300 yards in a north-easterly direction from the refuse heap, and, confining operations
to a certain circumscribed area, assisted in spreading of enteric fever; and that a second cloud
of flies was transferred some 500 or 600 yards to the north-west to the asylum, and there keeping strictly
within the limits of that institution, or rather, within the limits of a particular portion of that institution,
disseminated dysentery. For such cloud transmissions, the direction of the winds prevalent during the
summer affords no sufficient explanation, nor is it easy to frame a hypothesis to account for such localised
distribution of fly swarms; and further, the absence of recognition of the existence of enteric fever or
dysentery in the inhabited areas lying around and between the area of dysentery prevalence and that of
enteric fever prevalence (for, despite the suburban character of the locality, there are such inhabited
areas) is a fact which militates very strongly against the view that flies were responsible for either of
these outbreaks.
In summary of this matter, it may be stated that the facts at present ascertained, as to the
influence of flies in spreading disease under conditions obtaining in this country, are not such as to enable
any positive opinion to be expressed. There can be no question, however, as to the extent of the evil
caused by flies in the twelve centres studied during the past summer. The contamination of food
material, the irritation and annoyance and even loss of sleep caused to residents in the neighbourhood
of these centres, constitute injurious influences of the most serious character. The extent of this annoyance
in a particular instance will be appreciated by a glance at the photograph on the opposite page,
which shows the number of flies caught in a small general shop during a period of 72 hours during the
hottest part of last summer. Fig. 1 depicts seven papers covered with flies, representing a total of
upwards of 5,000 flies caught in that period, in one room and doubtless more could have been caught
had more papers been exposed, for experience shows that comparatively little relief is afforded by these
fly-catching operations. The room in question was a small one, about 800 cubic feet in capacity, and
as fast as the flies were caught others streamed in to renew the supply; so that had fresh fly-papers
been continuously available, there can be no doubt it would have been possible in 72 hours to collect a
solid mass of flies of no inconsiderable dimensions; indeed, the catch for the entire summer, given an
unlimited supply of fly papers, may not unreasonably be thought of as constituting in total bulk
quite an appreciable percentage of the cubic capacity of the room.
Even when successive detachments of invading flies are persistently removed, this does not
altogether dispose of the difficulty associated with contamination by fly marks. In rooms which
had not been "done up" for some time, the evidence of the extent of fly nuisance during the past
summer was strikingly afforded by the dense accumulations of fly marks upon the walls and ceilings.
Fig. 2 represents a portion of the ceiling of a room which had been infested with flies for several
summers and shows the extent of material which gradually collects, as the result of the deposit of excreta
by swarm after swarm of flies.
While the mildness of the summer has rendered it one in which the amount of fly nuisance has
been, presumably, at a minimum, the extent of this nuisance in the neighbourhood of collections of
refuse, even under the exceptional conditions which obtained, is made quite obvious by this enquiry.
No doubt, a great deal could be accomplished by further perfecting the system of removal of house
refuse and stable manure, but the evidence obtained clearly teaches the lesson that premises closely
surrounded by houses should not be used for the purpose of collection of refuse material; further, within
a town no manipulations of refuse should be permitted, the material should be transferred direct
from the cart to the canal barge or railway truck, and should on no account be deposited in proximity
to dwellings, even for a short period.
W. H. HAMER,
Medical Officer (General Purposes).