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Dr. Brownlee finds the correlation between "exposure" to wind and phthisis mortality to be 5 in
1851-70 and "6 in 1891-1900 in the Okehampton district; for the district of Barnstaple the coefficient
of correlation is -67. There is, therefore, apparently some relationship between weather conditions
and phthisis death-rate, but -the stability of the correlation coefficient, taken in conjunction with its
smallness, suggests that a third factor has to be reckoned with. It will be seen from the table that in
the first period the "imperfectly exposed" parishes had a higher mortality than the" sheltered," and
the rate was even greater than that of the" exposed "areas, but this was not the case in the second
period; on comparing further the decrease in the mortality, from the earlier to the later period, it is
seen that the decline in the" sheltered" and "imperfectly sheltered" parishes was about the same,
while the rate for the "exposed" parishes actually increased. The exposure in these areas can, however,
scarcely have increased in the interval separating the two periods; and even if it had, the " imperfectly
sheltered" areas should have shown some evidence of the change. It is evident, therefore, that the
areas described as "exposed "have some other characteristic by which their phthisis death-rate is
governed, than that merely of exposure to the effects of westerly winds. In the census volumes for
1861 reference is made to the depletion of population in various parishes of Okehampton district, the
reason mainly being given as agricultural depression, and the class affected was principally the farm
labourer. Mention is also made of the amalgamation of small farms, and the introduction of agricultural
machinery, both factors ousting the farm labourer. On the other hand, in the later period some districts
show an increase of population, due to the proximity of Chagford and Okehafnpton to the moors and
the consequent influx of tourists. In Chagford the reopening of a woollen factory is mentioned, in the
1871 census, as accounting in part for an increase in the population of that parish and also of North
Tawton ; moreover, in the same volume reference is made to the influx of labourers engaged on the
construction of the railway to Okehampton. In the changes which the opening of the district by the
railway caused, the areas classified as "exposed " do not appear to have shared.
Local knowledge is, however, necessary to select the factor which has to be taken into account
in interpreting the rates shown in the table. It may, perhaps, be hazarded that "exposure" affects
the ands as well as the labourers upon them, decreasing the fertility of the soil, and rendering the
gathering of its products more difficult and precarious; at any rate, with the unqualified assent of
Dr. Brownlee to the conclusion that the London rates are in direct correlation with "social condition,"
or, as Dr. Brownlee terms it, the influence of" hygiene," a further examination of social conditions in
the Devonshire groups of districts must clearly be instituted before any safe deduction can be made
f om the Okehampton experience.
Influenza, cerebrospinal fever, poliomyelitis, and polioencephalitis (including encephaliti
lethargic a).
In last year's report account was given of the recent prevalences of June July and of NovemberDecember,
1918, and of February-March, 1919. It was suggested that all the above-named forms of
epidemic disease were manifestations of one and the same influence; and it was urged that the cause of
the change of type observed in these epidemic manifestations must be sought n the degree and extent
to which the particular population concerned is exposed to infection on the one hand and susceptible or
immunised by previous attack on the other. This thesis was illustrated by a study of previous prevalences
of the group of influenzal diseases, from the time of the English sweats of 1485-1551 onwards,
including all the recorded historical prevalences of epidemics of influenza preceded and followed by
" epidemics of ague"; it being argued that the remarkable related agues consisted of the fevers with
gastro-intestinal, pulmonary or nervous complications, which are becoming recognised as constituting
the disease types the Proteus influenza is apt to assume. The relation of cerebro-spinal fever to influenza
was considered, and it was stated that the like association of the Heine-Medin disease with influenza
had been similarly instigated by Dr. Crookshank. This writer has expressed himself as follows:—
"Careful enquiry has satisfied me that Dr. Hamer is right in stating that the association of
diverse epidemics of myelitis, poliomyelitis, mesencephalitis and encephalitis with epidemics of
'influenza' has obtained not merely for years but for centuries. Change of type there has been, no
doubt, but changed conceptions of disease have also arisen, and we have got into the habit of speaking
as if a now conception of disease corresponded with a new appearance of disease or the appearance of
a new disease." (Proc. Roy. Soc. Med., Vol. XII., Discussion on Epidem. Enceph., p. xii.).
Dr. Crookshank has, moreover, added considerably to the body of evidence he had already
collected, in the course of the year which has elapsed since the date when his above quoted statement
was made.
Again, Dr. A. T. Nankivell (Jl. of the Roy. San. Inst., Vol. XL., No. 5) writes as follows:—" I
believe when we know more of the pathology of influenza, we shall find that the epidemic lethargic
encephalitis, polio-encephalo-myelitis, polyneuritis, botulism, and the diseases classified under the name
of the Heine-Medin gToup axe all due to the same microbe, namely, that of influenza. I believe, too,
although all the text-book scientists would be against me, that there is an intimate connection between
influenza and cerebro-spinal meningitis."
Further support for the view that cerebro-spinal fever is apt to prevail in close relation with
forms of illness classed as "pneumonia," "influenza," etc., was afforded by Col. Dorgan's report to
which reference will be made almost immediately. Again Dr. Crookshank informs me that Dr. D. M.
Lewis, of New Haven, Connecticut has published papers in which similar views are expressed. For
example, he writes (Boston Medical and Surgical Journal, Oct. 30, 1919, p. 540):—" Our known influenza
bacillus, the pneumococci, the streptococci, endemic the world over for centuries apparently, as also
epidemic, can explain epidemiologically and bacteriologically, pandemic influenza, if the term influenza
is not restricted to those cases or, as all of us have seen, epidemics due to the influenza bacillus."