Ok, all you dog lovers and dog writers, listen up. Lets get the facts straight. A dog has a knot at the back of his cock for one reason, to tie him to the bitch WHILE & AFTER he has/is unloaded his sperm inside her. It plugs her vagina up keeping the sperm inside, insuring pregnancy.
Look at a bitch the next time you see one - no, not your ex - the damn dog - canine species - four legged dammit. It's pussy is small. When they fuck, he pushes hard against her, slipping his doggie cock as far inside her as possible - BECAUSE - while IN THERE, his cock will expand to something HUGE as cocks go. It locks him to her. He and she cant't go anywhere untill his knot goes down.
So next time you have one of our canine friends fucking, his cock won't expand outside, it will expand inside. If it expands outside it won't go in - it's too damn BIG. UNLESS she had a reall BIG pussy. Yes - that's her, your ex - that bitch!
If you think you're hung, go look at a Great Dane. Those guys have huge cocks. John Holmes would have given them a second look. The knot at the back of one of those guys is humongous.
And no this does not come from personal experience.
Check your friendly vetrenarian and ask him/her to verify this. Make sure it's a female Vet!!! She'll be happy to explain it to you! In great detail. Tell her Tawny sent you.