Andrea Verrocchio, a leading Renaissance master of
that time. During this time da Vinci drew La valle del-
l’Arno(The Arno Valley) in 1473 and painted an angel
in Verrocchio’s Baptism of Christ(1475). In 1478 da
Vinci became an independent master. Da Vinci is
famous for his works of art such as the Mona Lisa, but
he is also as famous for his visionary drawings of
instruments and machines of the future. He was an
artist, scientist, engineer, and architect. He was also
one of the first to take detailed observations and to
experiment in a scientific manner.
In his later notebook the Codex Leicester,one
finds the largest assemblage of da Vinci’s studies relat-
ing to astronomy, meteorology, paleontology, geogra-
phy, and geology. It reveals that his profound
scientific observations far outweigh anyone else of his
time and documents his passion for research and
invention. His interest in light and shadow led him to
notice how the earth, moon, and planets all reflect
sunlight, for example.
The central topic of the Codex Leicester is the
“Body of the Earth” and in particular its transforma-
tions and movement of water. This study includes a dis-
cussion on the light of the moon, the color of the
atmosphere, canals and flood control, the effect of the
moon on the tides, and modern theories of the forma-
tion of continents.
He was well acquainted with knowledge about
his local rocks and fossils (Cenozoic mollusks) and
was uncannily prescient in his interpretation of
how fossils were found in mountains, theorizing that
they had once been living organisms in seas before
mountains were raised. Da Vinci contributed a
great deal of knowledge to human anatomy with
detailed drawings and notes in his anatomical
notebooks after having dissected some 19 human
cadavers.
Unfortunately, many of his scientific projects and
treatises were never completed, since he recorded his
technical notes and sketches in numerous notebooks
and used mirror script (his writing had to be read in a
mirror to be deciphered). It was centuries before the
genius of da Vinci was recognized. He died at the age of
67 on May 2, 1519, at Cloux, near Amboise, France.
Lepidoptera The taxonomic order that includes
butterflies, skippers, and moths. Butterflies have
antennae, compound eyes, six pair of legs, a hard
exoskeleton, and a body that is divided into a head,
thorax, and abdomen. The butterfly’s outer body is
covered by tiny sensory hairs and has wings covered
byscales.lesion Avisible region, such as a wound or fissure,
where there is abnormal tissue change in a body part; a
structural change due to wound, injury, or disease.lethal mutation A mutant form of a gene that
will result in the inviability (death) of the organism
if expressed in its phenotype. A conditional-lethal
mutation is lethal under one condition but not under
another.leukemia Cancer of the developing blood cells in the
bone marrow. The rampant overproduction of white
blood cells (leukocytes). A fatal cancer that is diag-
nosed yearly in 29,000 adults and 2,000 children in the
United States. There areseveral types of leukemia.
See alsoCANCER.leukocyte(white blood cell) A type of blood cell that
contains a nucleus but has no pigment. White blood
cells (WBC) are found in the blood and are involved in
defending the body against infective organisms and for-
eign substances. They are produced in the bone marrow
along with other types of blood cells. There are five
types of white blood cell within two main groups, and
each has its own characteristics. The polymorphonucle-
ar or granulocyte group comprises the neutrophils,
eosinophils, and basophils. The mononuclear group
comprises the monocytes and lymphocytes.
White blood cells are the main attackers of foreign
substances as part of the immune system.
Neutrophils move out of the blood vessels into the
infected tissue and engulf the foreign substances
(phagocytosis). Eosinophils migrate to body tissues and
release toxic substances to kill foreign substances.
Basophils, also called granular leukocytes, digest for-
eign objects from granules containing toxic chemicals.
Monocytes, which contain chemicals and enzymes,
ingest dead cells through phagocytosis and develop intoleukocyte 199