As a child, Clendening recalled his grandfather parading up and down the family street wearing a white rose in his buttonhole and vowing "confusion to the Hanoverian usurpers" every year on June 10.

He was called up on June 5, 1917, and served first as a captain, then a major at Fort Sam Houston in the U.S. Army Medical Corps.

[1][4] Clendening was the author of the successful book The Human Body, in 1945 it was noted that one and a half million copies had been sold.

He took interest in collecting old medical textbooks, researching the Shakespeare authorship question and studying the writings of Charles Dickens, and Arthur Conan Doyle's Sherlock Holmes stories.

[1] The University of Kansas Medical Center has described Clendening as "the greatest popularizer of Medicine in America in the first half of the twentieth century.