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Early in the nineties； when Dr。 Thayer and I were busy with the study of
malaria in Baltimore； we began experiments on the possible transmission
of the parasites； and a tramp； who had been a medical student； offered
himself as a subject。 Before we began； Dr。 Thayer sought information as to
the varieties of mosquitoes known in America； but sought in vain： there
had at that time been no systematic study。 The fundamental study which
set us on the track was a demonstration by Patrick Manson；＇3＇ in 1879； of
the association of filarian disease with the mosquito。 Many observations
had already been made； and were made subsequently； on the importance of
insects as intermediary hosts in the animal parasites； but the first really
great scientific demonstration of a widespread infection through insects
was by Theobald Smith； now of Harvard University； in 1889； in a study of
Texas fever of cattle。＇4＇ I well remember the deep impression made upon
me by his original communication； which in completeness； in accuracy of
detail； in Harveian precision and in practical results remains one of the
most brilliant pieces of experimental work ever undertaken。 It is difficult
to draw comparisons in pathology； but I think； if a census were taken
among the world's workers on disease； the judgment to be based on the
damage to health and direct mortality； the votes would be given to malaria
as the greatest single destroyer of the human race。 Cholera kills its
thousands； plague； in its bad years； its hundreds of thousands； yellow fever；
hookworm disease； pneumonia； tuberculosis； are all terribly destructive；
some only in the tropics； others in more temperate regions： but malaria is
today； as it ever was； a disease to which the word pandemic is specially
applicable。 In this country and in Europe； its ravages have lessened
enormously during the past century； but in the tropics it is everywhere and
always present； the greatest single foe of the white man； and at times and
places it assumes the proportions of a terrible epidemic。 In one district of
India alone； during the last four months of 1908； one quarter of the total
population suffered from the disease and there were 400；000 deaths
practically all from malaria。 Today； the control of this terrible scourge is in
our hands； and； as I shall tell you in a few minutes； largely because of this
control； the Panama Canal is being built。 No disease illustrates better the
progressive evolution of scientific medicine。 It is one of the oldest of
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known diseases。 The Greeks and Graeco…Romans knew it well。 It seems
highly probable； as brought out by the studies of W。H。S。 Jones of
Cambridge； that； in part at least； the physical degeneration in Greece and
Rome may have been due to the great increase of this disease。 Its clinical
manifestations were well known and admirably described by the older
writers。 In the seventeenth century； as I have already told you； the
remarkable discovery was made that the bark of the cinchona tree was a
specific。 Between the date of the Countess's recovery in Lima and the year
1880 a colossal literature on the disease had accumulated。 Literally
thousands of workers had studied the various aspects of its many problems；
the literature of this country； particularly of the Southern States； in the first
half of the last century may be said to be predominantly malarial。 Ordinary
observation carried on for long centuries had done as much as was
possible。 In 1880； a young French army surgeon； Laveran by name；
working in Algiers； found in the microscopic examination of the blood that
there were little bodies in the red blood corpuscles； amoeboid in character；
which he believed to be the germs of the disease。 Very little attention at
first was paid to his work； and it is not surprising。 It was the old story of
〃Wolf； wolf〃； there had been so many supposed 〃germs〃 that the
profession had become suspicious。 Several years elapsed before Surgeon…
General Sternberg called the attention of the English…speaking world to
Laveran's work： it was taken up actively in Italy； and in America by
Councilman； Abbott and by others among us in Baltimore。 The result of
these widespread observations was the confirmation in every respect of
Laveran's discovery of the association with malaria of a protozoan parasite。
This was step number three。 Clinical observation； empirical discovery of
the cure； determination of the presence of a parasite。 Two other steps
followed rapidly。 Another army surgeon； Ronald Ross； working in India；
influenced by the work of Manson； proved that the disease was transmitted
by certain varieties of mosquitoes。 Experiments came in to support the
studies in etiology； two of those may be quoted。 Mosquitoes which had
bitten malarial patients in Italy were sent to London and there allowed to
bite Mr。 Manson； son of Dr。 Manson。 This gentleman had not lived out of
England； where there is now no acute malaria。 He had been a perfectly
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healthy； strong man。 In a few days following the bites of the infected
mosquitoes； he had a typical attack of malarial fever。
＇3＇ Journal Linnaean Society； London； 1879； XIV； 304…311。
＇4＇ Medical News； Philadelphia； 1889； LV； 689…693； and monograph
with Kilborne； Washington； 1893。
The other experiment； though of a different character； is quite as
convincing。 In certain regions about Rome； in the Campania； malaria is so
prevalent that； in the autumn； almost everyone in the district is attacked；
particularly if he is a newcomer。 Dr。 Sambon and a friend lived in this
district from June 1 to September 1； 1900。 The test was whether they
could live in this exceedingly dangerous climate for the three months
without catching malaria； if they used stringent precautions against the
bites of mosquitoes。 For this purpose the hut in which they lived was
thoroughly wired； and they slept under netting。 Both of these gentlemen； at
the end of the period； had escaped the disease。
Then came the fifth and final triumphthe prevention of the disease。
The anti…malarial crusade which has been preached by Sir Ronald Ross
and has been carried out successfully on a wholesale scale in Italy and in
parts of India and Africa； has reduced enormously the incidence of the
disease。 Professor Celli of Rome； in his lecture room； has an interesting
chart which shows the reduction in the mortality from malaria in Italy
since the preventive measures have been adoptedthe deaths have fallen
from above 28；000 in 1888 to below 2000 in 1910。 There is needed a
stirring campaign against the disease throughout the Southern States of
this country。
The story of yellow fever illustrates one of the greatest practical
triumphs of scientific medicine； indeed； in view of its far…reaching
commercial consequences； it may range as one of the first achievements of
the race。 Ever since the discovery of America； the disease has been one of
its great scourges； permanently endemic in the Spanish Main； often
extending to the Southern States； occasionally into the North； and not
infrequently it has crossed the Atlantic。 The records of the British Army in
the West Indies show an appalling death rate； chiefly from this disease。 At
Jamaica； for the twenty years ending in 1836； the average mortality was
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101 per thousand； and in certain instances as high as 178。 One of the most
dreaded of all infections； t