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habitants of the area ate Mr. X's fried fish, at least 88 per cent. of those attacked by enteric fever did
so; indeed, excluding cases grouped in columns 1 and 2 for reasons already given, and including
as consumers of Mr. X's fried fish the cases 23, 39, 63, 70, 71 and 105, for the reasons which have
also been already specially discussed, the 88 per cent. becomes 100 per cent.
In making their house to house inquiry the inspectors took a census of the inhabitants of
the houses visited and ascertained particulars as to consumption of fried fish by each individual
included in their census. From these particulars diagram III.* on the annexed page, which
gives the facts as to fried fish consumption by males and females at different age periods, has been
constructed. Two points are specially noticeable in this diagram—
(a) The age distribution of the entire population is a somewhat unusual one, and
particularly noteworthy is the smallness of the number of representatives of certain
intermediate ages ; this is especially marked in the age group 25-35.
(b) It is clear that there is an undue preponderance of persons eating fried fish at
ages 5-20 years. This fact appears partially attributable to (a) and partially to manifestation
of a greater tendency to consume fried fish at those ages than at the earlier or
later age periods.
In conjunction with this diagram, diagram IV. beneath it may also be referred to. This
shows the result of observations kept upon the fried fish shop during those hours of the day when
frying was proceeding.† It will be seen that the persons purchasing were divided according to
whether they themselves ate or merely carried fried fish away with them; a third group
comprises those concerning whom there is doubt as to which of the other groups they should be
included in. The following points may be noted concerning diagram IV.—
(a) Consumers at ages 5-20 predominate; indeed, the disproportion between consumers
at those ages and those at other ages is now seen to be more marked than in the
upper diagram, doubtless not merely because there is a greater proportion at 5-20 years
of age of persons who eat fried fish, but because persons at the ages 5-20 years purchase
fried fish more frequently than persons at other ages, and therefore form a larger proportion
of the people found leaving the shop on any one day.
(b) The proportion borne by persons who themselves ate to the total number of
persons who purchased at different age groups is higher at the ages 5-20 than at other ages.
The height of the red columns may perhaps be taken as the best indication available of
fried fish consumption at different ages ; it certainly corresponds more closely to the actual
facts as to such consumption than do the complete columns, which include persons who
may have visited the shop merely to fetch fried fish for other persons.
Two minor points may be here noted. In the upper diagram the total number of persons
at ages 0-5 is seen to be less than at ages 5-10. This is probably accounted for by the fact that
the inspectors in inquiring concerning age, did not distinguish between age last birthday and age
next birthday. Any error arising on this account would tend to be more or less compensated for
in later age groups, but in the 0-5 age group there would of course be under-statement of the
number of persons in the group.
Again, in the lower diagram the height of the columns for the ages 15-20 is excessive.
From the nature of the observation kept it was impossible to do more than guess at the age of the
persons leaving the shop. There has clearly been a tendency to over-estimate the ages of persons
between 10 and 20; probably a few lads and girls at ages 13 and 14 have been transferred in this
way to the group 15-20. It is further probable that this error has operated to a greater extent
with young girls than with young lads, and this is borne out on comparing the heights of the
columns for females between 10-15 and 15-20 respectively with those of males at the same ages,
for if the excess of females over males at the latter age is accounted for by transference from the
former age, this would explain the deficiency of females as compared with males in the earlier age
group.
Broadly the facts ascertained by the two methods, first of house to house inquiry, and
second of keeping observation on the fish shop, confirm one another and indicate a considerable
preponderance of fried fish eaters at the ages 5-20. It has been already noted that the incidence
of the outbreak of enteric fever was especially upon these ages. The blackened columns at the
lower part of diagram IV. give the age and sex distribution of the cases which may be regarded
as constituting the special outbreak. The age and sex distribution of notified cases of enteric
fever in London as a whole in the year 1899 has already been given (for the purposes of comparison
with the age and sex distribution in the special outbreaks) in diagram I.
The correspondence between the exceptional age incidence of the disease and the preponderance
of persons at the ages specially attacked among the consumers of fried fish is a striking
one. In the absence of accurate knowledge as to relative susceptibility to the disease at different
ages under equal conditions of exposure, it is not of course possible to calculate exactly what
proportion of cases should occur at each age if fried fish from the shop to which the above observations
relate were the medium of infection, but it is interesting, in this connection, to contrast this
outbreak with the water-borne outbreak at Newport which occurred in 1894, the
milk-borne outbreak at Plumstead in 1895, and the outbreak in South-east London
in 1891, attributed by Dr. Geo. Turner to ice-cream. It will be found that while
in all four outbreaks there is markedly exceptional incidence upon ages under 25,
in Southwark this incidence is particularly excessive at ages 10-20, while, in the other outbreaks,
it is manifested to a relatively larger extent at younger ages. This fact is important in the light
of the knowledge obtained as to the ages especially represented among fried-fish eaters.
* See the second footnote on page 12.
† The observations relate to the morning frying 12 to 2 of a Wednesday, and the evening frying 7 to 12 of
a Friday.