252 BACOT : MOSQUITOES AND THE DANGER OF MALARIA.
well as numerous other important people. Among those who
suffered from malaria contracted in England was Nelson.
When old writers mention Ague, there is usually doubt as
to whether they are always referring to the same disease, the
word having been sometimes used as a general term to denote
fevers. Where, however, in past epidemics, the symptoms are
definitely mentioned, there is less difficulty now than was
formerly the case in identifying the ague spread by mosquitoes
in the light of the fuller knowledge of the symptoms of malaria
obtained recently in tropical lands.
Commentators and medical historians who lived before the
discovery of the plasmodium responsible for the disease, being
unaware of the protean nature of the symptoms, were unduly
inclined to disallow records, unless certain restricted clinical
signs, by which they were accustomed to identify ague, were
noted definitely.
The disease seems to have been endemic from an early period
in the Fens and low-lying districts of the counties of Cambridge,
Huntingdon, Lincoln, and parts of the adjoining counties. It
was also very prevalent in the low lands and marshes bordering
the rivers and estuaries in the south-east and south of England,
with an isolated centre of infection in the Bridgwater district
of Somersetshire. This distribution is shown on the accom-
panying chart (fig. 8). From these foci, the disease spread,
during seasons favourable to its increase, into the surrounding
districts, very greatly extending its areas in epidemic form.
There is some evidence that Ague was possibly not an
indigenous disease ; for William of Malmesbury, writing in the
twelfth century, speaks of the fens as then healthy. This is
in marked contrast to the remarks concerning the general un-
healthy character of these areas by writers in later centuries.
It may be surmised that, although the mosquitoes able to spread
the disease were indigenous, malaria itself was not introduced
until after the Norman Conquest.
Up to the middle of the nineteenth century, the disease was
still very prevalent, even in London. The proportion of Ague-
cases in relation to the total of in and out patients treated at St.
Thomas's Hospital in the years 1852 to 1858 ranged from 12.3
up to 46.5 per 1,000. During this same period, the proportion of
deaths from Ague in relation to deaths from all other causes