Because the dogs in this world there are many large species. Therefore, the scholars to divide the layout design is a group of dogs, so easy to learn and easy to remember lol.
Since dogs in this world has a very diverse species. So scholars would have to divide dogs into groups. To simplify the study And easiest to remember it
Because in this world there are many species of dog very much. So he had to break the dog scholars into groups. So easy to study, and easy แก่การ remembered.