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STENSEN, NIELS, also known as Nicolaus Steno
(b. Copenhagen, Denmark, 1%6111 January 1638; d.
Schwerin, Germany, 25 November/5 December
1686), anatomy, geology, mineralogy.
founded knowledge, and he was critical of analogies
and purely authoritarian statements. He also
asked for frequent observations and correct conclusions,
and he declared himself in favor of Descartes's
method in order to secure the greatest possible
certainty. Stensen's writings also contain
many passages that show a deeply religious nature
and a highly ethical character.
During the second half of his life, in which he
attained the highest fame and then - for the sake of
God and of human souls - renounced his scientific
research, there can be differentiated, both in time
and in subject matter, four great periods of research.
Each period began with almost accidental
individual observations but led to an abundance of
important discoveries and basic laws, many of
which were recognized only in later centuries.
The first of these periods was devoted to the
glandular and lymphatic system. In April 1660,
three weeks after his arrival at Amsterdam, where
he studied under the direction of Gerhard Bläes
(Blasius), Stensen made his first known discovery:
while dissecting the head of a sheep, he found the
duct of the parotid gland (Stensen's duct), which is
a principal source of saliva for the oral cavity.
In Leiden, then the most important university on
the Rhine, Stensen sought contact with the two
leading medical professors: Johannes van Horne,
who independently of Pecquet had discovered the
chief thoracic lymph passage, and Franciscus Sylvius,
famous as an iatrochemist and for his studies
on the brain. A warm and stimulating friendship
with Jan Swammerdam also began in Leiden. Soon
after Stensen's arrival, van Horne demonstrated on
humans the course of the parotid duct and declared
it to be Stensen's discovery, although Blasius, in
his Medicina generalis (1661), not only claimed it
for himself but incited his friends to slander Stensen,
his former student. There ensued a long quarrel
that Stensen settled both objectively and devastatingly
in his Apologiae prodromus (1663).
The controversy spurred Stensen to the further
investigation of the glands. He wrote: “I owe
much to the famous man Blasius because he not
only gave me cause to assert my property rights,
but also to discover other new things.”
The glands and lymph vessels were then a new
and exciting subject for investigation. In 1622
Aselli had demonstrated the lacteal vessels in the
mesentery of a dog; in 1642 Johann Georg Wirsung
had shown the excreting duct of the pancreas;
and in 1651 Pecquet had demonstrated the cisterna
chyli and its continuation, the thoracic lymph
duct; he also had realized that the latter poured its
contents into the veins. In 1653 Thomas Bartholin
demonstrated the thoracic lymph passage and the
lymphatic system in humans. He also showed that
the lymph vessels connecting the liver to the thoracic
duct carried lymph away from the liver,
thereby throwing doubt on the Galenic doctrine
that blood originated in the liver. When Thomas
Wharton published his systematic presentation of
the contemporary theory of glands in his Adenographia
(1656), he announced the discovery of the
duct of the submaxillary salivary gland; he also
designated the brain and tongue as glands.
In contrast, Stensen very soon advanced from
his “little discovery,” as he called his first one, to a
basic understanding of the whole glandular lymphatic
system, which he counted among the most
sublime artifices of the Creator. Without changing
the names of the conglomerate and conglobate
glands, the terms by which Sylvius had already distinguished
the anatomical form of the real glands
from that of the lymph nodes, Stensen distinguished
them according to their function. Arguing
against such contemporaries as Bils, Anton Deusing,
and Everaertz, on the basis of his observations
Stensen stated in his Leiden dissertation (1661):
I gather from this that the saliva consists of the
fluid secreted in the oral glands from the arterial
blood which is carried through the lymph ducts with
the aid of the Spiritus animales [a term then used for
the nerves] into the mouth and the closely adjoining
muscles, but that the round or conglobate glands in
the proximity carry the lymphs received from the
outer parts back to the veins so that it becomes mixed
with the blood streaming back to the heart.
This discovery led Stensen to consider every
fluid in the body as a glandular secretion. He then
found a series of glands furnishing fluid to each of
the body cavities. He likewise sought the afferent
and efferent ducts of secretion. Stensen still used
the name “lymph” for all watery glandular secretions,
because he was not yet able to differentiate
between them and to specify them chemically and
physiologically.
In the course of this basic research Stensen presented
in his Leiden dissertation new discoveries
of glands in the cheeks; beneath the tongue; and in
the palate, whose structure of veins, arteries,
nerves, and lymph vessels he also described. In his
Observationes anatomicae (1662), dealing with his
new discoveries concerning the glands, he described
the lachrymal apparatus in great detail.
Stensen determined the purpose of the lachrymal
fluid - to facilitate the movement and cleansing of