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the ages 3-, 4- and 5-. There is undoubtedly suggestion of some common cause operating at these
ages to produce parallel results with regard to the three diseases—measles, whooping cough and
diphtheria. In the case of diphtheria it will be observed that the increase also affects the age 10-,
but that this is not manifest in measles or whooping cough. The number of deaths from these
diseases at this age is, however, very small.
It is difficult to explain the fact that scarlet fever has not been affected in a similar manner at
these ages. Transference from diphtheria to scarlet fever, if proportionate at each age, would have
the effect of increasing the incidence of scarlet fever mortality on the earliest years of life, and would
in this way tend to obscure the result of increased incidence on ages 3-, 4- and 5- due to other cause,
such as that which has produced this increase in the other diseases. Whether it will be subsequently
found that the increasing feebleness of the scarlet fever virus, shown by the decrease in mortality, is
operating to prevent this cause from being manifested, the experience of future years alone can prove.
Apart from some such explanation as the above, it would be necessary to assume that the cause which
produced these changes in the other diseases was for some reason inoperative in the case of scarlet
fever."
It will be observed that the present diagram shows that in the ease of measles and whooping
cough with decreasing mortality at "all ages" the curves for the periods 1891-1900 and 1901-5 still
maintain the characteristic features of the curves for antecedent periods when compared with the
period 1861-70—i.e., in respect of both diseases the mortality in the first two years of life has
declined less than at other ages; in the case of measles the decline at the school ages has also been
retarded, whereas in the case of whooping cough the maintenance of the mortality at the school age
compared with other ages is not so conspicuous. In this connection it should be pointed out that the
decline in the whooping cough death-rate at " all ages " has been much greater than the decline in
the "all ages" measles death-rate ; thus the whooping cough death-rate at " all ages " in the period
1901-5 was 59.8 per cent, below the corresponding death-rate in 1861-70, while the measles deathrate
in the period 1901-5 was only 21.9 per cent, below the corresponding death-rate in 1861-70.
Referring now to scarlet fever it will be observed that the curve of 1901-5 approximates closely to
a straight line, and no modification of the statement made in the 1897 report appears to be necessitated
by the later experience of the behaviour of scarlet fever in this respect. It should be noted,
however, that the period 1861-70 was one of excessive mortality, and that the scarlet fever deathrate
at "all ages " in 1901-5 was 91.6 per cent, below that of the period 1861-70, the decline being
considerably greater than that previously referred to in the case of whooping cough.
The experience of the behaviour of diphtheria in late years shows that while, as compared with
1861-70, the excessive incidence of mortality upon the school age is still a conspicuous feature in the
diagram it was in the period 1901-5 with a declining rate of mortality at" all ages," much less
marked than in 1891-1900., i.e., during a period of epidemic prevalence. It is worthy of note,
however, that notwithstanding the fact that the diphtheria death-rate at " all ages " in the period
1901-5 was 54 2 per cent, below the corresponding death-rate in the period 1861-70, the death-rates
at ages 5- and 10- were only 1.0 per cent., and 7.0 per cent, respectively below the rates at the same
ages in the period 1861-70,
The curves shown in the diagram suggest broadly that the incidence of mortality upon the
school age tends to become most marked in periods of greatest prevalence. Thus in the case of
measles the curve for the decennium of greatest prevalence, viz., 1881-90, shows the most marked
incidence on the school age-period of life as does that for the decennium 1891-1900 in the case of
diphtheria. It would therefore appear that in any estimate, as to the amount of observed increase in
the mortality in any periods compared, which can be thought of as associated with increase of school
attendance, account must be taken of the relative prevalence of the disease under consideration
in the two periods ; and probably also consideration would have to be had for the question whether
the tendency of the prevalence was in the direction of increase or decline.
In connection with the increased incidence of diphtheria mortality at the school age-period of
life referred to in the 1897 report, the following table shows that, whereas the diphtheria mortality
at " all ages " and at the age-period 3—15 years began to decline subsequent to the year 1893, and
has with but little interruption declined year by year since, the relatively increasing incidence of
diphtheria mortality on the age-period 3—15 years (the rate of mortality at " all ages " being taken as
100) was continued until the last three years during which it has been distinctly lower, while the
relative incidence of attack on the age period 3—15 years (the rate of attack at "all ages "being taken
as 100) appears to have been maintained up to the present time. It may be that the maintenance of
the relative incidence of attack on the school age, in spite of the fact that the relative incidence of
mortalityat that age has declined, is due to more complete inquiry for cases of this disease among schoolattending
children and, indeed, this view is supported by the fact that the case mortality at the ageperiod
3—15 years, which had for some years been showing in some degree greater decline than that
of " all ages," showed a more marked decline during the last three years. No definite opinion can,
however, be expressed upon this question which is rendered more complex by the introduction in
recent years of the treatment of diphtheria with antitoxic serum. The experience of the last three
years in London shows—
(a) decrease in the " all ages " rate of mortality.
(b) special decrease in the rate of mortality at ages 3—15 years.
(c) decrease in the case rate at " all ages " and at ages 3—15.
(d) a smaller decrease in the case rate at 3—15 years than at "all ages."
(e) a greater reduction in the fatality of cases aged 3—15 years than is observed at "all ages."
The decline in the "all ages" death rate referred to above is manifest also in the figures for 1903
and 1904 of England and Wales minus London. How much of this decline is due to the use of antitoxic
serum cannot be stated, but it may be mentioned that this remedy has been used in the hospitals of
the Metropolitan Asylums Board subsequent to the year 1894 and in increasing degree.
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