Concord, New Hampshire. In 1915 he went to Yale
University, left to become an air force pilot in 1918,
and returned to get his B.A. in 1920. He received a
Ph.D. at Harvard in 1930 for a thesis that presented
evidence that bacterial anaphylaxis and hypersensitivity
of the tuberculin type are distinct phenomena, and he
stayed at Harvard until 1946 as a teacher.
In 1938 Enders began the study of some of the
mammalian viruses and undertook, in 1941, in collabo-
ration with others, a study of the virus of mumps. This
work provided serological tests for the diagnosis of this
disease and a skin test for susceptibility to it. It also
demonstrated the immunizing effect of inactivated
mumps virus and the possibility of attenuating the viru-
lence of this virus by passing it through chick embryos.
It showed that mumps often occurs in a form that is not
apparent but that nevertheless confers a resistance that
is as effective as that conferred by the visible disease.
In 1946 Enders established a laboratory for
research in infectious diseases at the Children’s Medical
Center at Boston. The understanding of viruses at the
time was scant, and development of an antipolio vac-
cine depended on gaining the ability to grow sufficient
quantities of the polio virus under laboratory control.
The stumbling block was that poliovirus cultures could
be kept alive for a useful length of time only in nerve
tissue, and that was hard to obtain and maintain.
Enders, along with T. H. WELLERand F. C. ROB-
BINS, found that viruses could be grown on tissues
treated with penicillin to retard bacterial growth, and
they were also successful in growing mumps and polio
viruses as well. The ability to grow and study polio led
to the development of a vaccine later by Salk and
Sabin. The research opened the way to other vaccines
against highly contagious childhood diseases such as
measles, German measles (rubella), and mumps.
Enders, Robbins, and Weller shared the 1954 Nobel
Prize in medicine for this pioneering work.
Enders was a member of many organizations. Con-
sidered one of the most important contributors of the
20th century, Enders also provided insight to links
between viruses and cancer, and the pattern and pro-
cess of tumor growth. He died on September 8, 1985.
endocrine gland A ductless organ that produces and
secretes hormones into the bloodstream.
See alsoGLANDS.
endocrine system Acollection of glands that work
interdependently and produce hormones that regulate
the body’s growth, metabolism, and sexual develop-
ment and function. The endocrine system consists of:
two adrenal glands, located on the top of each kidney;
the pancreas, found in the abdominal cavity behind the
stomach; the parathyroid and thyroid, located at the
base of the neck; the pituitary, located at the base of
the brain; and the ovaries and testes, the female and
male sex glands.
Each of the endocrine glands produces hormones
that are targeted to a particular area of the body and are
released into the bloodstream and serve to regulate the
activity of various organs, tissues, and body functions.endocytosis A process by which liquids or solid par-
ticles are taken up by a cell through invagination of the
plasma membrane. The plasma membrane creates a
“well” in which the substances settle, become sur-
rounded, and are then pinched off into a vesicle that
can be transported through the cell.
See alsoPHAGOCYTOSIS;PINOCYTOSIS.endoderm One of three primary germ layers in
embryonic development (along with mesoderm and
ectoderm). The endoderm is the inner layer of cells and
gives rise to organs and tissues associated with diges-
tion and respiration.endodermis Aparenchyma tissue that regulates the
transport of materials into the vascular bundles of most
roots, stems, and leaves. It surrounds the vascular
cylinder; is especially prominent in roots; and has
suberized Casparian strips, a band of suberin (waxy
substance) within the anticlinal walls. It is the inner-
most layer of the cortex in plant roots.endogenous Originating internally. In the description
of metal ion COORDINATIONin metalloproteins, endoge-
nous refers to internal, or protein-derived, LIGANDs.endomembrane system The collection or network
of membranous organelles, such as the endoplasmicendomembrane system 113