Kari Alitalo had studied lymphatic vessels for more than two decades. So he knew that this network, which carries immune cells throughout the body and removes waste and toxins, didn’t extend into the brain: This had been accepted wisdom for more than 300 years. “Nobody questioned that it stopped at the brain,” says Alitalo, a scientist at the University of Helsinki in Finland.
"When Scientists Saw the Mouse Heads Glowing, They Knew the Discovery Was Big" is from the May 21, 2017 Health & Science section of The Washington Post. It was written by David Kohn and narrated by Sam Scholl.