When I was a graduate student taking William Breneman's course on endocrinology, I first heard the name Walter B. Cannon (1871-1945).  He coined the term homeostasis and applied it to the capacity of the body to maintain a steady state condition.  It used regulators such as temperature, hormones, nerve cell transmitters, and other means to regulate cell and organ activity.  His book, The Wisdom of the Body became a best seller.  He was born in Wisconsin to a railroad executive father and school teacher mother.  Raised as a Calvinist with a Huguenot ancestry, he broke with their rejection of science and became a Unitarian.  At Harvard medical school where he got his MD and taught physiology, he used x-rays in 1896 and applied them to study how animals swallow.  He also devised the "barium meal" to increase contrast between the organs and surrounding tissue.  He studied how animals went into shock from wounds and identified hormones associated with the "flight or fight" response to stress.  Later in life he championed scientific integrity by helping scientists escaping Nazi Germany and 

supported medical efforts to help the Spanish government in its war against Franco. He was nominated several times for a Nobel Prize. In his time he was considered the leading physiologist in the United States.