Nikolaos Steno - the man who laid the foundation for several different fields of science

Today marks the 374th birthday of Nils Stensen or in his Latin name Nicolaus Steno, who established the infrastructure of the sciences of geology and anatomy, and also discovered that the fossils are a link between the two worlds 

Google marked today the 374th anniversary of the birth of Nils Stensen, or in his Latin name Nicolaus Steno, a Danish anatomist and geologist (January 10, 1638 – November 25, 1686). Steno was one of the cluster men of the Renaissance, who made important contributions to two completely different fields of science and also developed a career in the Catholic Church. He made important discoveries in the human body on the one hand and on the other hand he dealt with fossils and minerals. Steno, the son of a goldsmith, was educated in Copenhagen before starting his travels and studies abroad in 1660.
While studying anatomy in Amsterdam, he discovered the tube that carries the saliva from the salivary glands to the oral cavity (a tube from the ear) known as Stensen's duct after his name.

Other important discoveries in anatomy stem from his understanding that muscles are composed of fibers and his demonstration that the isturbal gland also exists in other animals besides humans (René Descartes stated that the isturbal gland is the location of the soul and believed that both exist only in humans).

Steno received his medical degree from the University of Leiden in 1664 and a year later left for Florence, where he became physician to Duke Ferdinand II.

In the field of geology, he made important contributions to the study of crystals and fossils. His observations of quartz crystals showed that although the crystals differ in their external structure, they all have the same angles between the parallel faces (corresponding angles). This led to the formulation of Steno's law, which states that the angles between two parallel faces on a crystal of any chemical or mineral are consistent and characterize the type of crystal. Today they know that this is the result of a regular internal arrangement of the atoms or molecules that make up the crystal.

His views on geology and mineralogy were expressed in his 1669 book De solido intra solidum naturaliter contento dissertationis prodromus (Introduction to a discussion about solid bodies naturally contained within a solid). The odd title refers to the solid bodies we call fossils found inside other solid bodies. Steno was particularly concerned with fossils that came from the Mediterranean area that were known at the time as glossipetrae (tongue stones), some thought they fell from the sky and others thought they grew on the ground like plants. They were triangular, smooth, hard and had distinct slits along both sides.

In 1666 Steno saw the head of a large shark. He immediately noticed the similarity between the tongue stones and the shark's teeth. In an attempt to understand this correlation Steno formulated two basic principles to explain how solids are formed within solids. The first rule, the rule of order, proves that it is possible to tell which part solidified first by distinguishing which solid is pressing on another. When the tongue stones left their mark on the surrounding rocks they had to be formed first and therefore it makes no sense to think that they grew on the ground.

Steno's second law stated that if two solids were similar in all observable aspects, then they were formed in the same way. In other words, the similarity between shark teeth and tongue stones means that the tongue stones are remnants of teeth that have become extinct. This claim was considered revolutionary for its time.

However Steno's explanation encompasses not only the tongue stones but they offer a new way of interpreting the fossil record, which later geologists expanded on.

Another important contribution was to the understanding of the geological layers, even if in his time it was not assumed that the earth was so ancient.
In Wikipedia we find the following detail regarding the theory of layers:

• The principle of original horizontality: "A layer that is now perpendicular to the horizon or inclined to the horizon was once parallel to the horizon."
• The principle of superposition: "At the time when any layer was formed, all the material that was placed on it was in a liquid state, and therefore, at the time when the lower layer was formed, nothing from the layer above it existed." That is, the order of the layers is also the order in which they sank and except for situations of disturbance, the lower layers precede the upper ones.
• The principle of horizontal continuity: "The material that forms any layer spreads laterally in a continuous manner over the surface of the earth unless other solid bodies stand in its way"
• Cutting-crossing relationships and the principle of inverse relationships: "A body that creates a discontinuity by cutting through a layer must have been created after this layer was created".

Steno changed his religion from Lutheran to Catholic in 1667, became a priest and joined the Holy Order in 1675. In 1677 he was appointed bishop of Titopolis (in Turkey) and took care of the spiritual needs of the few Catholics who survived in Scandinavia and northern Germany.
In 1953, his grave was discovered with the remains of his body, except for a few bones, during excavations for the construction of a road near the Medici estate in Florence.