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The number of counties is small for the calculation of representative correlation coefficients,
but for the sake of comparison with the coefficients given by Dr. Brownlee, it may be mentioned that
the correlation of the proportion of males engaged in agriculture with the amount of " young adult "
phthisis is -86 ; of the same with the percentage of milk samples found tuberculous mimib '90; and with
the mortality under five years from tubercular peritonitis minus "94.
These correlation coefficients are all considerably higher than those obtained by Dr. Brownlee,
and suggest that the facts are to be explained, in some measure, by the contrast in occupation in
agricultural and urban employments respectively.
It will be noticed that the counties, from which the milk samples give the highest proportion
tuberculous, are those in which the process of urbanisation is more advanced. Possibly in highly
urbanised counties situated at a distance from London, the local urban centres compete with London
for the output, with the advantage of local knowledge. On the other hand the milk of the more
essentially rural counties has a relatively small local demand to meet, and in areas where transport by
rail is the only means of delivery, London is at no great disadvantage as compared with the large urban
centres of the Midlands, etc. The condition of the cattle in the rich pasturage of the plains is likely
to be better, and the farmers more prosperous, than is the case in the smaller holdings on less fertile
soil of higher ground.
The explanation of the high death-rate in rural areas among young adults given in my earlier
reports has been that the rural districts have for many years been drained by the urban centres of the
pick of their young adults, some of whom, however, may return when ill to die in the country ; while
in the urban population, on the contrary, the migration has resulted in a well-mixed stock, and some
of the phthisics have, up to recent years at any rate, often left the towns for the sake of their health.
To this it may be added that all the statistics point to the fact that the employments of rural districts
restrain the development of phthisis in the chief working years of life.
The influence A further question considered by Dr. Brownlee is that raised twenty years ago by Dr. Gordon,
of wmd ag £0 effect 0f exposure to damp or cold winds, in increasing susceptibility to pulmonary tuberculosis.
Phthisis Statistics bearing upon this point are very limited, and in his discussion of the subject Dr. Brownlee
mortality. relies mainly upon Dr. Gordon's records for the district of Okehampton during 1891-1900, supplemented
by figures, relating to the same district for the years 1851-70, and also for the district of Barnstaple
which Dr. Brownlee has himself abstracted. These are small districts, but the figures show, Dr.
Brownlee considers, a significant relationship between the incidence of phthisis mortality and the extent
of exposure to south-west or west wind. He sets out in detail the figures for Okehampton for the two
periods mentioned, and in the following table they are so arranged as to exhibit the marked difference
in mortality between " exposed " and " sheltered " districts respectively :—
The question at once arises in considering Dr. Brownlee's conclusions as to whether the death-rate
of a county is any criterion of the health of the cows in that county. The cows, it may be assumed, do
not in the main live in the county boroughs and crowded urban centres, which contribute so greatly
to the excess in the death-rate of highly urbanised counties. There is not, relatively speaking, the
same degree of difference between the death-rate of rural areas, situated in different counties, as is
found wben the county death-rate', are contrasted. The dominant factor, indeed, throughout is the
degree of urbanisation ; and to illustrate this the figures which Dr. Brownlee uses have been recast
into tabular form from the standpoint of " urbanisation," represented by the proportion per 1,000
occupied males classed as engaged upon agriculture in the census of 1911 :—
County.
Proportion
of males
engaged on
agriculture.
Phthisis mortality.
Young
adult.
Middle
age-
Mortality
from
tubercular
peritonitis.
Mean death-rates,
1911-14.
Urban
districts.
Rural
districts.
Per cent,
tuberculous
milk.
Oxfordshire 29.3 60 65 30 10 .90 10.40 3.1
Wiltshire 22.6 52 49 44 11 .42 10.25 8.7
Sussex 22.2 48 109 50 11.08 9.55 9.1
Somersetshire 21.5 57 78 41 10.95 10.67 8.4
Buckinghamshire 20.2 38 65 26 11 .62 10.35 4.4
Berkshire 19.7 40 70 40 11.10 9.95 5.9
Northamptonshire 19.7 64 63 44 11.17 10.87 4.4
Hampshire 15.4 44 121 64 10.90 9.97 10.9
Leicestershire 14.9 56 81 86 12.62 11.02 8.9
Essex 11.2 32 90 68 10.95 10.22 11.2
Derbyshire 8.1 27 64 116 13.43 12.27 15.6
Staffordshire 7.7 8 126 131 15.05 11.47 13.3
The number of counties is small for the calculation of representative correlation coefficients,
but for the sake of comparison with the coefficients given by Dr. Brownlee, it may be mentioned that
the correlation of the proportion of males engaged in agriculture with the amount of " young adult "
phthisis is .86; of the same with the percentage of milk samples found tuberculous mimib '90; and with
the mortality under five years from tubercular peritonitis minus .94.
These correlation coefficients are all considerably higher than those obtained by Dr. Brownlee,
and suggest that the facts are to be explained, in some measure, by the contrast in occupation in
agricultural and urban employments respectively.
Climatic character of
district in regard to W.
and S.W. winds.
'"Sheltered"
"Exposed"
" Imperfectly sheltered "
Population.
5,484
1,079
2,864
1851—70.
Phthisis mortality
per 1,000.
2.11
2.6
3.1
Population.
4,080
831
2,362
1.20
3.37
1.5
Phthisis mortality
per 1,000.
1891-1900.