Old Dog's Tail

My mother has kept this tip of my old dog's tails since I was in primary school.

When my sister left the house for school she didn't realise the dog had followed her so accidentally closed the door on her tail. It was only the tip and she was okay in the end, but for some reason my mother kept the severed tip.

I remember saying I saw the bone of her tail at school, to which a classmate replied "Dog tails don't have bones."