And fourthly, careful inspection of the siftings of
the straw disclosed living parasites, small mites,
which when applied to the skin quickly produced the
characteristic eruption.
SANITATION
When the thoughtful historian gets far enough
away from the nineteenth century to see it as a whole,
no single feature will stand out with greater distinctness
than the fulfilment of the prophecy of Descartes that
we could be freed from an infinity of maladies both
of body and mind if we had sufficient knowledge of
their causes and of all the remedies with which nature
has provided us. Sanitation takes its place among
the great modern revolutions—political,
social and intellectual. Great Britain deserves
the credit for the first practical recognition of
the maxim salus populi suprema lex. In the middle
and latter part of the century a remarkable group
of men, Southwood Smith, Chadwick, Budd, Murchison,
Simon, Acland, Buchanan, J.W. Russell and Benjamin
Ward Richardson, put practical sanitation on a scientific
basis. Even before the full demonstration of
the germ theory, they had grasped the conception that
the battle had to be fought against a living contagion
which found in poverty, filth and wretched homes the
conditions for its existence. One terrible disease
was practically wiped out in twenty-five years of
hard work. It is difficult to realize that within
the memory of men now living, typhus fever was one
of the great scourges of our large cities, and broke
out in terrible epidemics—the most fatal
of all to the medical profession. In the severe
epidemic in Ireland in the forties of the last century,
one fifth of all the doctors in the island died of
typhus. A better idea of the new crusade, made
possible by new knowledge, is to be had from a consideration
of certain diseases against which the fight is in
active progress.
Nothing illustrates more clearly the interdependence
of the sciences than the reciprocal impulse given
to new researches in pathology and entomology by the
discovery of the part played by insects in the transmission
of disease. The flea, the louse, the bedbug, the
house fly, the mosquito, the tick, have all within
a few years taken their places as important transmitters
of disease. The fly population may be taken as
the sanitary index of a place. The discovery,
too, that insects are porters of disease has led to
a great extension of our knowledge of their life history.
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
