According to Cecil's Straight Dope:
Is it true that Thomas Edison's last breath is preserved in a test tube at the Henry Ford Museum outside Detroit? --Listener, Mike Murphy show, KCMO radio, Kansas City, Missouri
What's with you guys in KC? Einstein's brain wasn't enough? As a matter of fact, Edison's last breath is preserved at the Henry Ford Museum, after a fashion. Ford was a great admirer of Edison's, having once served as chief engineer at the Detroit Edison Company; later the two became fast friends. Ford re-created Edison's Menlo Park workshop in Greenfield Village, the collection of historic buildings next to the Ford museum, and it's possible he wanted to re-create Edison himself, after a manner of speaking. Supposedly Ford asked Edison's son Charles to hold a test tube next to his father's mouth when he breathed his last in 1931. Ford's motive for this odd request is obscure. He is known to have been interested in reincarnation, and some say he thought the spirit exited the body with one's last breath; ergo, what he was collecting was essence of Edison, no doubt for reconstitution at some later date. Others say he just wanted a souvenir of his departed buddy. Whatever the case, it's likely that any Edisonian vestiges, if in fact there ever were any, have long since leaked out. The tube was discovered in the Ford family home in 1950 after both Henry and his wife had died. It's now on display at the Ford museum, just in case you wanted to make any last-minute amendments to your vacation plans.