Friend, the black color in the vomit is digested blood. As your son could see today, he is bleeding the upper gastrointestinal tract, I am sorry. Having a history of eating a bone I would want to rule out the bone being obstructed in the gastrointestinal tract. Could there be other causes? Yes. But, given how serious an obstructed bone could be it is important to rule this out. Unfortunately, not much your son will be able to do at home. Enzo will need to see a veterinarian for x-rays as an initial screening test. If the bone is obstructed and Enzo is not treated (surgery) the outcome is likely fatal, I am sorry. I realize that this answer may not be entirely to your liking, and I regret being the bearer of information that you really don’t want to hear. But it would be unfair to you and unprofessional of me were I to provide you with anything less than truthful and honest information. I hope you understand. In the meantime, this is what he can do:
1- Do not give things like Pepto Bismol or Imodium. Start him on Pepcid AC (famotidine) 10mg tablet every 12 hours. You can buy Pepcid AC over the counter in any pharmacy.
2- No food or water for 8-12 hours. Need to give his gastrointestinal tract time to rest.
3- After 8-12 hours offer a small amount of water. Wait half hour, if no vomiting, offer a small amount of rice (50%) and boiled boneless chicken or ground beef (50%) 4-6 times a day. Keep on this diet for several days then wean into regular diet.
Note: If he is going to see a vet in the morning best to leave him without food.
4- Follow up with his family veterinarian for a hands on examination and x-rays. If cost is a concern look into his local ASPCA or Shelter where they often offer veterinary services at a lower cost.
My goal is to provide you with excellent service - I hope I've provided the information you were seeking, if you feel you have received anything less, please reply back as I am happy to address follow-up questions. Kindly rate me when you are done.