Webster's New World Medical Dictionary

da Vinci, Leonardo
The father of anatomic art,
as well as an accomplished architect, scientist, engi-
neer, inventor, poet, sculptor, and painter. In strik-
ing contrast to the pronouncements of Galen and
other anatomists, da Vinci recognized that optimal
scientific knowledge of human anatomy could be
gained only by dissecting the human body. He
injected the blood vessels and cerebral ventricles
with wax for preservation, a technique that is still
used today. His drawings of the human anatomy
have long been considered to be unrivaled.
dacryocyst
The lacrimal sac; tear sac. The dilated
(widened) upper end of the nasolacrimal duct, the
passageway that allows tears to drain into the nasal
cavity.
dactyl-, -dactyl
Prefix or suffix denoting the dig-
its (fingers or toes), as in dactylitis (inflammation of
a finger or toe).
dactyledema
Swelling of a finger or toe.
dactylitis
Inflammation of a finger or toe.
dactylomegaly
Enlargement of a finger or toe.
dactylospasm
A cramp of a finger or toe.
Daily Prayer of a Physician
A prayer that is said
to have been written by the twelfth-century physician–
philosopher Moses Maimonides, but possibly penned
by German physician Marcus Herz. This prayer is
often recited by new medical graduates.
Daltonism
See 
red-green colorblindness.
dander
Tiny scales shed from human or animal
skin or hair. Dander floats in the air, settles on sur-
faces, and makes up a good portion of household
dust. Cat dander is a common cause of allergic
reactions.
dandruff
A scalp condition that produces white
flakes that may be shed and fall from the hair. One
cause of dandruff is overworking of the sebaceous
glands. Another cause of dandruff is fungus, espe-
cially an abundance of the fungus Pitrosporum
ovale. If several weeks of using a good-quality sham-
poo does not stop the dandruff, treatment options
include an antifungal shampoo such as Denorex,
DHS Targel, ionil-T plus, MG217, Neutrogena T/Gel,
Scalpicin, Sebulex, Selsun Blue, Tegrin, or Zircon.
The active ingredients approved for dandruff treat-
ment by the US Food and Drug Administration
(FDA) include tar, pyrithione zinc, salicylic acid,
selenium sulfide, sulfur, and ketoconazole.