15. John Scott Haldane
Scottish-born scientist John Scott Haldane studied the physiology of breathing and learned the effects of dangerous gases on the mind and body by experimenting on himself. One notable case was the time he locked himself in an airtight box for eight hours and breathed the same air over and over again he noted the effect this had on him. He also poisoned himself with carbon monoxide to see what would happen. As a result he came up with the idea of using canaries to detect the lethal gas as their bodies were affected much faster.