The term stress was first popularized by endocrinologist Hans Selye (1936). As a young medical student, Selye noticed that patients who were hospital- ized for many different illnesses often had similar symptoms, such as mus- cle weakness, a loss of weight and appetite, and a lack of ambition. Maybe these symptoms were part of a generalized response to an attack on the body, he thought. In the 1930s, Selye tested this hypothesis by exposing laboratory rats to various stressors, including heat, cold, heavy exercise, toxic substances, food deprivation, and electric shock. As anticipated, the different stressors all produced a similar physiological response: enlarged adrenal glands, shrunken lymph nodes, and bleeding stomach ulcers. Borrowing a term from engineer- ing, Selye called the reaction stress—a word that quickly became part of every- day language.