How do you know if your dog is mad or sad?

Sometimes dogs become depressed because they lose a companion; often the only treatment for this is time and still being a companion to him. If your dog appears to be depressed, try spending more one-on-one time with him - going for walks just you and him, sitting with him and petting just him, etc. Most dogs eventually realize that they still have a "pack" and are still welcome in it given time.