Spurred on by the specter of miraculous cures to horrible diseases, Irving Weissman, director of Stanford’s Institute for Stem Cell Biology and Regenerative Medicine, is working on experiments combining human brains and mice. The Stanford Daily reports that Dr. Weissman “has worked with the transfer of human neurons to the brains of mice for several years now. He has already bred mice whose brains are composed of 1 percent human neurons, finding that transplanted human brain cells could successfully connect to a mouse brain.” Such experiements yield what are known as “chimeras,” the creation of organisms composed of material from multiple species.




