What were William Clark's responsibilities during the expedition?

Clark also served mainly as the expedition "doctor" and co-writer of the Journals. He often traded medical care for food and eventually established a reputation among the natives for his skills. Finding a man with a tumor on his thigh who couldn't walk, Clark cleansed and dressed the wound and left him some soap to wash the sore. He soon got better and as Clark says "this man assigned the restoration of his leg to me."