Malpighi's Forgotten Drawings of Renal Glomeruli

Marcello Malpighi (1628-1694) is universally recognized for his pioneering work in microscopic anatomy. His groundbreaking studies of human, animal, and plant anatomy laid the foundation for modern histology, embryology, comparative anatomy, entomology, botany, and biology. Among his many contributions is the discovery of renal glomeruli, which he described as minimae glandulae (very small glands), attributing to them the production of urine. His treatise De renibus contained a detailed description of glomeruli but no images. A drawing of glomeruli by Malpighi appeared many years later in an illustrated manuscript sheet containing a plate with different types of glands, including the kidney's minimae glandulae. While examining Malpighi's handwritten scientific diary, kept at the Biblioteca Universitaria di Bologna, we found unpublished drawings of his kidney observations, including one that may represent his earliest extant depiction of glomeruli. We review Malpighi's groundbreaking discovery of glomeruli, focusing on his kidney drawings and their historical significance.