Marcello Malpighi was a prominent Italian physician and biologist. Born in 1628 near Bologna, Italy, he studied medicine and philosophy at the University of Bologna, graduating in 1653. Malpighi was among the first and most impactful investigators to use the newly invented microscope for biological exploration. His work helped transform medicine from a field reliant on ancient texts to one grounded in direct observation and empirical evidence.
Completing the Puzzle of Blood Circulation
Before Malpighi, William Harvey proposed in 1615 that blood circulates in a closed system. Harvey described blood flow from arteries through the heart and lungs, but he could not observe how blood transitioned from the smallest arteries to veins. This missing connection left a gap in understanding the circulatory system.
Malpighi addressed this gap through his microscopic observations, especially on frog lungs. In 1661, he first visualized and described a network of minute, hair-like vessels connecting the arterial and venous systems. He named these tiny vessels “capillaries,” derived from the Latin word “capilla” meaning “little hair”.
His observations, detailed in his 1661 work “De pulmonibus observationes anatomicae,” provided the evidence Harvey lacked. His discovery showed blood flowed through these microscopic conduits, completing the circulatory circuit, rather than leaking into open spaces as previously believed. This advanced physiological understanding, demonstrating a continuous, closed system of blood flow.
Microscopic Investigations of Organs
Beyond his work on blood circulation, Malpighi applied the microscope to investigate the fine structures of human organs. His observations uncovered unknown anatomical features, many now bearing his name. This broadened the understanding of human anatomy.
In the kidney, Malpighi identified and described the structures now known as renal corpuscles, the initial filtering components of nephrons. These spherical structures filter blood. In the spleen, he observed lymphoid nodules, often called Malpighian bodies. These are integral to the spleen’s immune functions.
Malpighi also made observations on the liver, where he described the organization of its lobules, the liver’s functional units. His work on skin revealed a deeper layer responsible for color, known as the Malpighian layer. He also identified taste buds on the tongue, contributing to understanding sensory organs.
Exploring the Anatomy of Plants and Insects
Malpighi’s scientific curiosity extended beyond human anatomy to plants and insects. He showed the microscope’s universal applicability for biological discovery, venturing into largely unexplored fields. His work laid foundations for future studies in botany and entomology.
In entomology, he notably studied the silkworm (Bombyx mori), publishing a detailed anatomical study in 1669. This was one of the earliest comprehensive investigations into an invertebrate’s internal structures. He described the complex respiratory system, identifying the network of tracheae (small holes in the insect’s skin), which showed insects do not use lungs for breathing.
His botanical investigations, in his two-volume Anatome Plantarum (1675-1679), were equally groundbreaking. He used the microscope to reveal the intricate internal organization of plants. He provided the first detailed descriptions of stomata (tiny pores on leaves that regulate gas exchange) and produced drawings of plant stem and root structures.
Establishing the Field of Histology
Marcello Malpighi’s enduring impact stems from his methodical approach to biological investigation, not just his discoveries. By consistently applying the newly available microscope to study the fine structures of living organisms, he established a new scientific discipline: microscopic anatomy, now known as histology. This systematic use of magnification allowed for the examination of tissues at a level previously unimaginable.
His work provided an anatomical basis for understanding physiological processes, shifting scientific inquiry towards observable, empirical data. Malpighi’s research, often communicated through letters, attracted the attention of the Royal Society in London. He was invited to correspond with them in 1668, and many of his findings were published in their Philosophical Transactions. This collaboration helped disseminate his methodologies and cemented his standing as a founder of this new scientific field.