nt we must rely upon
the intelligence of individuals to recognize the advantage to
themselves, their families, and their employers, of knowing that their
bodies do not harbor hidden enemies of vitality and efficiency. From a
semi-annual examination of teeth to a semi-annual physical examination
is but a short step when once its effectiveness is seen by a few in
each community.

[Illustration: THE OLD SOUTHFIELD, NOW ANCHORED AT BELLEVUE
HOSPITAL'S DOCK, NEW YORK CITY, GIVES DAILY LESSONS IN THE
PREVENTABLE TAX LEVIED BY TUBERCULOSIS]

Ignorance of one's physical condition is a luxury no one can afford. No
society is rich enough to afford members ignorant of physical
weaknesses prejudicial to others' health and efficiency. Every one of
us, even though to all appearances physically normal, needs the
biological engineer. New conditions come upon us with terrific
rapidity. The rush of work, noise, dust, heat, and overcrowding of
modern industry make it important to have positive evidence that we
have successfully adapted ourselves to these new conditions. Only by
measuring the effects of these environmental forces upon our bodies can
we prevent some trifling physical flaw from developing into a chronic
or acute condition. As labor becomes more and more highly specialized,
the body of the laborer is forced to readapt itself. The kind of work a
man does determines which organs shall claim more than their share of
blood and energy. The man who sets type develops keenness of vision and
manual dexterity. The stoker develops the muscles of his arms and back,
the engineer alertness of eye and ear. All sorts of devices have been
invented to aid this specialization of particular organs, as well as to
correct their imperfections: the magnifying glass, the telescope, the
microscope, extend the powers of the eye; the spectacle or an operation
on the eye muscles enables the defective eye to do normal work. A man
with astigmatism might be a policeman all his life, win promotion, and
die ignorant of his defect; whereas if the same man had become a
chauffeur, he might have killed himself and his employer the first
year, or, if an accountant, he might have been a chronic dyspeptic from
long-continued eye strain. It is a soul tragedy for a man to attempt a
career for which he is physically unadapted.[11] It is a social tragedy
when men and women squander their health. A great deal of the success
attributed to luck and opportuni