dog doctor

A famous dog-doctor was ſent for, and undertook to cure the patient, provided he might carry him home to his own houſe;

As I saw my glorious, patient dog, my faithful companion in many a long, lone journey, my deliverer, humanly speaking, from many a dangerous blizzard storm, thus dying slowly before me, I did long for wise old Rover, the famous dog doctor of my wounded dogs in other days.

Referring to a dog who acts as a doctor for other dogs, thus sense 1 also applies.