Who is "Jock" as noted in the memoir, All Things Bright and Beautiful?

Jock is a dog who always chases James off his owner's property after James pays a veterinary visit. Unlike most dogs Jock takes this game very seriously. When his owner has him bred and his puppies threaten to outrun him, Jock's pride takes a serious hit. Jock's owner sells the puppies, however, and Jock is able to return to his position as king of his home.