The Med Series — Murray Leinster

Roving through the uncharted vastness of deep space, Med Serviceman Calhoun of the Interplanetary Medical Service brings his mission of healing to isolated colonists far from Earth.

Alone in his starship with only his pet tormal for companionship, Calhoun plunges into an uncharted void without stars or nebulae...discovers a planet whose inhabitants starve to death amid a bounty of food...and dares a quarantined world ruled by galactic untouchables!