Answer: Caspar Wistar

Caspar Wistar was once one of the premier physicians in Philadelphia. Born in the city in 1761, Wistar was the son of Richard and Sarah Wyatt Wistar, a Quaker family. As a teenager, Wistar assisted the wounded during at the Battle of Germantown in 1777, and this experience reportedly inspired him to go into medicine. He studied at the University of Pennsylvania and the University of Edinburgh, Scotland, and received his doctorate in 1786. For the remainder of his life, Wistar worked as a physician in Philadelphia, alongside other doctors such as Benjamin Rush. He served the College of Physicians and worked for the Pennsylvania Hospital and the University of Pennsylvania.  

In 1803, Meriwether Lewis, who had been chosen to lead the expedition into the American West, visited Philadelphia to meet with Rush and Wistar, at President Thomas Jefferson's behest. Jefferson hoped that Rush and Wistar, both members of the American Philosophical Society, could educate Lewis and better prepare him for the journey. Wistar agreed to tutor Lewis in medicine and paleontology. After the Lewis and Clark Expedition, Wistar assisted in the examination of specimens they brought back. 

Image: Portrait of Caspar Wistar, photograph (undated)