Every exquisite drawing by Santiago Ramón y Cajal, the founder of modern neuroscience, is marred by a curious mark. Here is the little-known story behind it.
About the author
R. Douglas Fields is a neuroscientist and an international authority on brain development and the cellular mechanisms of memory. He is the author of the books The Other Brain and Why We Snap, and he is an adjunct professor of neuroscience and cognitive science at the University of Maryland.