How do I ask him to help?

My dog has fleas and a skin rash so I decided going to the vet this afternoon would be good. The issue is that the cost is around 112 for the visit, shot, and flea pill. The dog was bought by me and my now ex boyfriend months ago. He lives with me because my ex already has 6 other dogs (i dont know why he wanted to get another one). The ex hardly cares for the dog (one time he had kennel cough and he was too lazy to drive to the pharmacy to buy him anything) and he never asks how he is or visits. But when it comes to the dogs health and comfort, I inform the ex and expect him to help since he is partially the owner. We have not talked in a while so I do not know how to approach him. I also do not know if he is willing to pay half ($66) or take us (since my brother takes my car until 6pm). I dont think it is fair that I do everything on my own when he was the one insisting to get a puppy together.