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REPORT OF THE MEDICAL OFFICER OF HEALTH,
1909-
PART I.
The mean temperature of the air during 1909 was somewhat below the average of the preceding
65 years. The monthly average was exceeded in October, April, December and January, while in
June the temperature was markedly below the average, the deficiency being also considerable in
September, March, February and July. The rainfall during the year, as a whole, was above the average,
the excess being most marked in the months of June, March and October: the deficiency was greatest
in November and January, the other months below the average being February, May, and August.
The marriage rate (15 8) was below the marriage rate of the preceding year (15.9), and was the lowest
rate recorded in London since complete marriage statistics have been available. The birth-rate (24.2)
was the lowest on record in London since the institution of civil registration, as was also the infantile
mortality (108). The death-rate (14.0) was, however, slightly higher than in the preceding year. The
deaths from pneumonia, influenza, cancer and measles were above the annual average of the preceding
10 years, and the deaths from small-pox, whooping-cough, scarlet fever, diphtheria, enteric fever,
diarrhoea, and phthisis were below the average.
If the death-rate in 1909 be compared with that of the decennium 1891-1900, the result expressed
in terms of lives and "life-capital," shows a saving of 24,902 lives, representing a gain to the community
of 1,080,784 years of " life-capital."
Population.
The population of the Administrative County of London, estimated to the middle of the year
1909, was 4,833,938.
The population of the City of London and of each metropolitan borough, as constituted
by the London Government Act of 1899, estimated to the middle of 1909, is shown in the following
table—

In the consideration of these estimates and of the rates which in this report are based upon
them, it is necessary to bear in mind that 1909 is the eighth year which has elapsed since the enumeration
of the population in 1901.
Natural Increase (Excess of births over deaths).
The natural increase of the population is the amount by which the number of births exceeds the
number of deaths annually. It is a convenient measure for comparing the vitality of one
community or section of a community with another. Immigration and emigration to some
extent affect the comparison of the natural increase of various towns, but their effect upon the
natural increase rate is partially compensated for by the fact that if the emigration exceeds the
immigration, both the deaths and the births are reduced, while if immigration exceeds emigration, both
are increased, thus these factors need not influence greatly the difference between the birth-rate
and death-rate (i.e., the rate of natural increase) except so far as the age and sex of the immigrants
differs widely from that of the emigrants. A comparison of the rates of natural increase in different
localities is also affected by the differences in the age- and sex-constitution of the populations
compared. The combined effect of all these disturbing factors, however, will probably not be so
great as to vitiate general comparison of the crude natural increase rates.
The following table shows the mean annual rate of natural increase of the population per 1,000
living in certain periods from 1876-80 to 1909:—
2067 B