Malpighi, Marcello
3/10/1628–8/29/1694
ITALIAN
PHYSICIAN
In the second half of the seventeenth century, Marcello Malpighi used the newly invented microscope to make a number of important discoveries about living tissues and structures, earning himself enduring recognition as a founder of scientific microscopy, histology (the study of tissues), embryology, and the science of plant anatomy.
Malpighi was born at Crevalcore, just outside Bologna, Italy. The son of the owners of a small plot of land, Malpighi studied medicine and philosophy at the University of Bologna. While at Bologna, Malpighi was part of a small anatomical society headed by the teacher Bartolomeo Massari, in whose home the group met to conduct dissections and vivisections. Malpighi later married Massari's sister.
In 1655 Malpighi became a lecturer in logic at the University of Bologna. One year later, he assumed the chair of theoretical medicine at the University of Pisa. In 1659 he returned to Bologna as lecturer in theoretical, then practical, medicine. From 1662 to 1666 he held the principal chair in medicine at the University of Messina. Finally, in 1666, he returned again to Bologna, where he remained for the rest of his teaching and research career. In 1691, at the age of sixty-three, Malpighi was called by his friend Pope Innocent XII to serve as the pontiff's personal physician. Reluctantly, Malpighi agreed and moved to Rome, where he died on November 29, 1694, in his room in the Quirinal Palace.
Early in his medical career, Malpighi became absorbed in using the microscope to study a wide range of living tissue—animal, insect, and plant. At the time, this was an entirely new field of scientific investigation. Malpighi soon made a profoundly important discovery. Microscopically examining a frog's lungs, he was able for the first time to describe the lung's structure accurately—thin air sacs surrounded by a network of tiny blood vessels. This explained how air (oxygen) is able to diffuse into the blood vessels, a key to understanding the process of respiration. It also provided the one missing piece of evidence to confirm William Harvey's revolutionary theory of the blood circulation: Malpighi had discovered the capillaries, the microscopic connecting link between the veins and arteries that Harvey—with no microscope available—had only been able to postulate. Malpighi published his findings about the lungs in 1661.
Malpighi used the microscope to make an impressive number of other important observations, all "firsts." He observed a "host of red atoms" in the blood—the red blood corpuscles. He described the papillae of the tongue and skin—the receptors of the senses of taste and touch. He identified the rete mucosum, the Malpighian layer, of the skin. He found that the nerves and spinal column both consisted of bundles of fibers. He clearly described the structure of the kidney and suggested its function as a urine producer. He identified the spleen as an organ, not a gland; structures in both the kidney and spleen are named after him. He demonstrated that bile is secreted in the liver, not the gall bladder. In showing bile to be a uniform color, he disproved a 2,000-year-old idea that the bile was yellow and black. He described glandular adenopathy, a syndrome rediscovered by Thomas Hodgkin (1798–1866) and given that man's name 200 years later.
Malpighi also conducted groundbreaking research in plant and insect microscopy. His extensive studies of the silkworm were the first full examination of insect structure. His detailed observations of chick embryos laid the foundation for microscopic embryology. His botanical investigations established the science of plant anatomy. The variety of Malpighi's microscopic discoveries piqued the interest of countless other researchers and firmly established microscopy as a science.