Volunteers wore body-covering suits made up of hollow tubes. Hot water was circulated through the tubes to heat the surface of the skin, thereby increasing body temperature. Volunteers swallowed a tiny thermometer so that the temperature inside the body could be measured accurately. The suits did not cover the volunteers' heads, arms, and feet, and researchers measured sweating and blood flow through the skin by using volunteers' forearms. Volunteers were asked about their level of discomfort when body temperature increased. For each volunteer, a low dose of cocaine or a nonnarcotic local anesthetic (lidocaine) dissolved in saline solution was applied to the inside of the nose. Each of the solutions was given in separate trials, but neither the volunteers nor the doctor knew which substance was being given or in what order.