There's a gland just inside the dogs anus. When it gets full and the dog can't express the fluid on it's own, a qualified person (Vet.) will use his finger to manually express the fluid for the dog.Yep, It's as gross as it sounds.
What Is Anal Squeezing For A Dog?
I used to eat that when I was a child...and now that I am grown ...it smells like a bait shop...but I still love to shoot a anus worm or two out just for old times sake