Basic Information

"Leonard H. McCoy, MD, was a noted physician and scientist of the 23rd and 24th centuries. An accomplished surgeon, physician, psychologist, and exobiologist, he was also considered an expert in space psychology. As ship's surgeon and chief medical officer, he served aboard the USS Enterprise and USS Enterprise-A for a combined 27 years."

http://memory-alpha.org/en/
wiki/Leonard_McCoy