Who is Doc from Cannery Row and what is their importance?

Doc is the owner/operator of Western Biological Laboratories, Doc collects and preserves sea creatures for shipping to research facilities nationwide. He is "deceptively small", strong, passionate, and charismatic. He wears a beard in an era when facial hair is rare and, fearing water on his head, normally wears a rain hat. Doc is interested in everything, makes wisdom out of nonsense, and is the source of philosophy, science, and art. He rushes about helping epidemic victims, delivering food, and enlisting Dora Flood's girls to sit with the scared and hopeless. Doc sleeps little during this time, and lives on beer and canned sardines.