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It must now be noted that the prevalence of diphtheria in the affected area which is under consideration,
was accompanied by a special incidence of the disease upon children at school ages. This
fact may be rendered evident in several ways.
I. In the first place comparison maybe made between the behaviour of diphtheria in the area affected
during the period of special prevalence, and its behaviour in this area at other times. During 1893,
1894, 1895 and the first 36 weeks of 1896, 83 cases of diphtheria and membranous croup were notified
in the " affected area." In 82 of these cases the age of the patient is specified, and of these 82 notifications,
15 related to infants from 0-3 years of age, 48 to children between 3 and 12 years of age, and 19 to
persons aged 12 and upwards. On the other hand, of the 91 notifications received from the same
area during the 37th-44th weeks of 1896, 13 related to infants from 0-3 years of age, 67 to children
between 3 and 12 years of age, and 11 to persons aged 12 and upwards. Thus, whereas the percentage
of sufferers in each of the three age periods was for the period from 1893 to the 36th week of 1896—
18.3 per cent. in the case of infants 0-3.
58.5 „ „ children 3-12.
23.2 „ ,, persons aged 12 and upwards.
the corresponding percentages for the period from the 37th-44th weeks of 1896 were—
14.3 per cent. in the case of infants 0-3.
73.6 „ „ children 3.12.
12-1 „ ,, persons aged 12 and upwards.
The special incidence upon children at ages 3 to 12 in the recent outbreak is here apparent, but
the question may be studied in another manner.
II. The notifications of diphtheria in the whole of London during the years 1893-4-5 have
been analysed by the medical officer of the Council, and grouped according to the ages of persons
attacked. By making use of these results, and of the census figures, the attack rates from diphtheria
per 1,000 living at the several age periods in London can be obtained. These rates may be compared
with the rates obtaining in the affected area during the recent outbreak. It is necessary for the purpose
of making such comparison to know the population at the several age periods in the affected area. Now
the affected area comprises five enumeration districts, and it has therefore been possible to learn the age
constitution of its population at the time of the 1891 census. Further, it has been possible to
obtain the total population in these five enumeration districts at the census of March, 1896, By applying
the former results to the latter the numbers for the several age periods in 1896 are obtained. The age
distribution of the London population is given in the census returns for certain defined periods of
years, and it has been necessary, therefore, in proceeding to make the comparison in contemplation,
to deal with these periods. It is for this reason that in the annexed table the figures for the age
periods 3-12, and 12 and upwards have not been given, but those for the periods 3-10, 10-15,
and 15 and upwards, have been quoted. It will be found, however, that the new division into age
periods throws a further light upon the age incidence of diphtheria in Lewisham during the weeks in
which the recent outbreak occurred.

From this table it is clear that children at the age period 3-10 have been specially attacked
during the recent diphtheria prevalence in Lewisham, for when the case rate at all ages is taken as
100, it transpires that the Lewisham rate for the age 3-10 is nearly one-third greater than that of
the London rate for the same age period, while the Lewisham rates for the three other age periods
dealt with (0-3, 10-15, and 15 and upwards), fall markedly below the London rates.
III. So far all cases notified have been dealt with, and no attempt has been made to discriminate
between primary attacks in particular houses and secondary cases occurring in households which had
been already invaded. There is advantage, however, in further considering the matter from this point of
view, for the age incidence observed in the case of persons primarily attacked is to be looked upon as
furnishing an important indication of any peculiarities in the age distribution of the disease.
Again, comparison has been made, in a series of reports upon outbreaks of diphtheria published
in the reports of the medical officer of the Local Government Board, between the age distribution of the
cases primarily occurring in families, and " behaviour of throat illness towards persons of various ages
in the families that had become invaded." This method of inquiry furnished, in the absence of a large
number of recorded notifications from which attack rates could be deduced, a particularly valuable