Malpighi supplied the final link in understanding the circulation of the blood. Galen described the 4 chambers of the heart and the connecting valves. He believed that arterial blood and venous blood communicated via pores in the interventricular system. Other anatomists, in particular Servetus and Colombo, described the pulmonary circulation in anatomic terms, but how the system functioned still remained a mystery. Fabricius of Aquapendente discovered the venous valves, allowing blood to flow only in the direction of the heart, and William Harvey put it all together in De Motu Cordis. He described the circulation as efferent from the left side of the heart, afferent into the right side of the heart, the 2 sides communicating through the pulmonary or minor circulation. It was still uncertain, however, how arterial blood made its transit into the venous system, a question conveniently ignored by Harvey. Malpighi squared the circle with his histological description of capillaries in frog and tortoise lungs and in the toad bladder. He observed the transit of “red globules” from artery to vein in in vivo preparations. He founded the science of microscopic anatomy, and is generally thought of as the “father of histology.”
Malpighi was born in Crevalcore, near Bologna Italy, on March 10, 1628. He was raised on a farm. He entered the University of Bologna at 17 years of age, but was forced to abandon his studies for more than 2 years to settle family affairs when his father, mother, and paternal grandmother all died within months of each other. He was granted doctorates in medicine and in philosophy in 1653. Upon graduation, he applied for a position as lecturer at Bologna, but it was 3 years before the post was awarded. He became a lecturer in logic. Contemporaneously, he was offered the first chair in Theoretical Medicine at the University of Pisa, which he accepted. He remained in Pisa for 3 years. It was in Pisa that Malpighi met and befriended Giovanni Borelli, a mathematician and polymath interested in animal movement among other more abstract things. Borelli exerted a powerful effect on Malpighi's scientific outlook and became a mentor for, and collaborator with Malpighi for the remainder of his life.
After 3 years in Pisa, Malpighi returned to Bologna, claiming family pressures and poor health as the reasons. Three years later, on the recommendation of Borelli, he was again offered a professorship at another university, Messina. Again, Malpighi took the job and was appointed as a Professor Primus in Medicine. He remained there for 4 years and then returned to Bologna for the last time. He remained there for the next 25 years until, in 1691, in failing health, he was appointed as the personal physician to Pope Innocent XII. He died of a stroke in Rome on September 30, 1694.
During his student age at Bologna, Malpighi was one of a few select students invited to attend private dissections and vivisections by Bartolomeo Massari, University Professor, and leading anatomist of his time. In 1654, Malpighi married Francesca Massari, the younger sister of the great anatomist. She died a year later, but Malpighi's life as an anatomist was entrained.
Malpighi's first article appeared in 1661. It was published as 2 letters to his friend Borelli, “De pulmonibus.” In this landmark article, Malpighi described the anatomy of the frog lung, bronchioles, alveoli, and the pulmonary capillary bed. In these capillaries, he could see, in vivo, “red globules” moving from arterioles to venules. The capillary bed was the final concept required to solidify the concept of the circulation of the blood. This and other articles were noticed by Henry Oldenburg, Secretary of the Royal Society of England. Oldenburg asked if Malpighi would correspond with him, and Malpighi became the first Italian fellow of the Royal Society. From this time forward, most of his discoveries were published in the proceedings of the Royal Society.
He studied the development of the chicken embryo. He was convinced that he could see the form of the chick in unfertilized eggs. This became an important force in the “predelineation” movement. Of course, it was one of Malpighi's scientific errors. Malpighi's study of the liver, spleen, and kidney convinced him that organs are composed of glandular structures, corpuscles that, in aggregate, constitute the organ. He described the renal corpuscle (nephron), the splenic corpuscle (lymphoid centers), and the hepatic secretory unit. He studied insects and described the trachea through which insects breathe. He made a comprehensive study of the silkworm (De Bombyce). He studied the clotting of blood (de polypo cordis). He was the first person to describe the erythrocyte. He studied neuroanatomy and concluded that the brain is an endocrine organ. He studied plants and described the annular rings and deduced their function. The great Swedish botanist, Linnaeus named a genus of plants after Malpighi, the Malpighiaceae.
The last decade of Malpighi's life was accompanied by challenge and criticism as often the case for scientific pioneers. Pope Innocent XII intervened and invited him to Rome in 1691 as papal archiater (first physician) to the Pope. He was further honored by election to the College of Doctors in Medicine and with a teaching appointment in the Papal Medical School. He died September 30, 1694. He is buried in the church of Santi Gregorio e Siro in Bologna. The inscription on the marble tablet over his tomb says, “Summum Ingenium, Integerrimam Vitam, Fortem Strenuamque Mentem, Audacem Salutaris Artis Amorem,” (great genius, honest life, strong and tough mind, audacious love for the medical profession).