Joseph Bell was a teacher at the medical school of Edinburgh University in the 19th century.
In his instruction, he emphasized the importance of close observation in drawing diagnosis. To illustrate it, he would often pick a stranger and describe what he concluded the person was, the occupation and recent activities from what he observed with the person. Sir Arthur Conan Doyle's Sherlock Holmes character is loosely based on Joseph Bell. Dr. Bell was aware of this inspiration and took some pride in it.