adrenal gland. He shared with Edward C. Kendall and
Tadeus REICHSTEINthe 1950 Nobel Prize in physiolo-
gyor medicine for this pioneering work in the treat-
ment of rheumatoid arthritis with cortisone and
ACTH.
He authored many papers in the field of rheuma-
tology, received numerous awards, and belonged to
several scientific organizations throughout his life. He
died on March 30, 1965, in Ocho Rios, Jamaica.
hepatic portal vessel A system of veins that delivers
blood from glands and organs of the gastrointestinal
tract (GIT) to the liver. A portal vein enters the liver at
the porta hepatis and distributes venules and sinusoids,
capillarylike vessels where blood becomes purified,
before it goes into the inferior vena cava. The hepatic
artery carries oxygen-rich blood to the liver from the
heart and mixes with the portal vein in the sinusoids.
Thus two filtering systems, the capillaries of the GIT
and sinusoids of the liver, perform their tasks on the
blood.
herb Partof a plant that is used for medicinal, food,
or aromatic properties.
herbivore An animal that only eats plants to obtain
its necessary nutrients for survival.
See alsoCARNIVORE.
hermaphrodite Anindividual with both male and
female sexual reproductive organs and that functions
as both male and female, producing both egg
and sperm. The individual can be a simultaneous
hermaphrodite, having both types of organs at the
same time, or a sequential or successive herm-
aphrodite that has one type early in life and the other
type later. If the female part forms first it is called pro-
togynous hermaphroditism; it is called protandrous
hermaphroditism if the male forms first.
Some examples of hermaphrodites are most flukes,
tapeworms, gastrotriches, earthworms, and even some
humans.
In plants, it is when male and female organs occur
in the same flower of a single individual.
hernia A protrusion of a tissue or organ or a part of
one through the wall of the abdominal cavity or other
area. A hiatal hernia has part of the stomach protrud-
ing through the diaphragm and up into the chest and
affects about 15 percent of the human population.Herodotus A Greek who lived ca. 400 B.C.E. and
observed fossil seashells in the rocks of mountains. He
interpreted these remains as once-living marine organ-
isms and concluded that these areas must have been
submerged in the past.Hess, Walter Rudolf(1881–1973) SwissPhysiolo-
gist Walter Rudolf Hess was born in Frauenfeld, in
Aargau Canton, Switzerland, on March 17, 1881, to a
teacher of physics. He received a doctor of medicine in
1906 from the University of Zurich.
Originally he began his career as an ophthalmolo-
gist for six years (1906–12), but dropped his practice
and turned to the study of physiology at the University
of Bonn. In 1917 he was nominated director of the
Physiological Institute at Zurich, with corresponding
teaching responsibilities, and later director of the Physi-
ological Institute (1917–51) at the University of
Zürich.
He spent most of his life investigating the responses
of behavior, respiration, and blood pressure by stimu-
lating the diencephalon of cats using his own tech-
niques. He was awarded the Nobel Prize in 1949 for
his work related to the diencephalon.
Among Hess’s books is The Biology of Mind
(1964). He died on August 12, 1973.heterochromatin Most cell nuclei contain varying
amounts of functional (active) and nonfunctional (inac-
tive) DNA. Functional DNA is called euchromatin,
while nonfunctional or inactive is called heterochro-
matin. The latter is DNA that is so tightly packaged it
cannot transcript. Two forms exist: constitutive hete-
rochromatin, where portions of the chromosome are
always inactive, and facultative heterochromatin,
where portions of the chromosome are active in some
cells at one time but are inactive now (such as the Y
chromosome and Barr bodies). A gene is closed or inac-
cessible and not expressed if it is heterochromatin.heterochromatin 161