The Precocious Discovery of Erythrocyte Deformability: Giuseppe Saverio Poli's 18th-Century Insight

This article re-examines the historical work Elementi di Fisica Sperimentale (Elements of Experimental Physics, Venice, 1796) by Giuseppe Saverio Poli (1746–1825) to contextualize and emphasize his pioneering contribution to 18th-century microscopy and physiology. The analysis focuses, in particular, on Poli’s observations regarding red blood cells (erythrocytes). While the scientific polemic of the era (involving figures like Della Torre, Fontana, and Caldani) centered on the controversial static shape of the erythrocyte, Poli offered a unique dynamic description: he observed how red blood cells were forced to disintegrate into particles, align, and immediately reform to traverse extremely narrow passages ("stretto angustissimo"). This description, obtained with the primitive microscopes of the time, surprisingly anticipates the principle of erythrocyte deformability (or cell squeezing)—a fundamental mechanism for microcirculation and the passage of blood cells through capillaries, the validity of which was definitively confirmed only by sophisticated 21st-century microfluidic experiments. This paper establishes Poli not merely as a meticulous educator of Experimental Physics, but as a precursor whose acute observations laid the groundwork for modern applied biophysics.