Steno was the first to demonstrate that muscles do not increase in volume when they contract. This refuted the longstanding Galenic theory and laid the foundation for modern muscle physiology. With the present work, Steno fully developed his developed his groundbreaking muscle theory and revolutionized our knowledge of how the muscles function. He also included comparisons between animal and human anatomical structures, helping to establish the discipline of comparative anatomy and opening new pathways for later evolutionary thought.

It as also in the present work that Steno, through the dissection of a shark's head, successfully identified "tongue stones" as fossilized shark teeth, which directly contradicted earlier beliefs that fossils formed spontaneously in rocks. This marked a foundational moment in paleontology and stratigraphy helping to establish that fossils are remains of once-living organisms, thereby setting the stage for his later geological principles (in “De solido intra solidum naturaliter contento”, 1669), such as the principle of original horizontality and superposition.
Steno studied rock formations and concluded that all rocks and minerals were once fluid, settling into horizontal layers over time. These layers could trap and preserve animal remains as fossils with older layers at the bottom and newer ones on top - a principle now known as Steno’s Law of Superposition. While others had suggested that fossils were once-living organisms, Steno advanced the idea by linking fossils to specific moments in Earth’s history and showing that rock layers formed gradually. His insights laid the foundation for modern geology and paleontology helping to reveal how life evolved over billions of years.

“The first part of Stensen’s "Elementorum" elaborates upon the concepts introduced in his "De musculis et glandulis", laying the foundation of muscular mechanics. In collaboration with the mathematician Vincenzo Viviani, a pupil of Galileo, Stensen developed a geometrical description of muscular contraction, and attempted to show theoretically that muscles did not increase in volume during contraction. Dealing with his subject on a strictly mechanical basis, he gave a clear terminology for the parts of the muscle and characterized muscle and muscle fiber according to their geometrical structure. He recognized that muscle tension was the result of the individual forces of its constituent fibers and was thus able to refute the views of Borelli, who believed that a muscle’s hardness and swelling during contraction was due to the influx of nerve fluid.

The remainder of the treatise includes Stensen’s account of his dissection of a shark’s head. In discussing the relationship of the shark teeth to similar-shaped fossil stones found in the Mediterranean, Stensen developed theories of how geological structures and fossils might be formed. This has been called the first outline of a scientific theory of the development of the earth. The Elementorum also contains two of Stensen’s embryological contributions, his recognition of the egg-producing function of the mammalian ovary and his description of the placenta in the viviparous shark.” (Norman 2012).

“A Danish physician, geologist, and clergyman, Steno studied medicine at Copenhagen, Leiden and Paris. He settled in Italy, first as professor of anatomy at Padua and then in Florence as house physician to Grand Duke Ferdinand II. He served for at brief time as professor and royal anatomist in Copenhagen. Dissatisfied, he returned to Florence where he abandoned his scientific career and entered the priesthood, eventually becoming bishop.” (Heirs of Hippocrates)

The present work is a superb testament to Steno’s multifaceted life and eclectic career, revolutionizing several different branches of science. His fundamental scientific method applied here also reveals Steno as, not only a brilliant observer, but also a methodological pioneer, who helped shape how science was conducted in the early modern period.

Norman 2012
Garrison-Morton 577
Osler 4021
Waller 9223
Barchas 1994