Carl Lange was a Danish physician and psychologist, born in 1834 and known for his contributions to the field of psychology. He is best recognized for developing the James-Lange theory of emotion, which posits that emotions arise from physiological responses to stimuli. This theory suggests that we feel emotions because of our body's reactions, such as increased heart rate or sweating. Lange's work laid the groundwork for understanding the connection between the mind and body. He collaborated with American psychologist William James, and together they influenced the study of emotions in psychology. Lange's ideas continue to be relevant in contemporary discussions about emotional responses and their physiological underpinnings.