A.F.
i agree with bite him back. 19 months old is not too young. i broke my son of biting me at 8 monyhs by biting him back after all else failed to stop it. i had tried crying- he thought it was funny. i tried time out - useless. i tried stern voice - useless (he has autism - he does not distinguish voice tones as having any meaning). he bit me one day and i got tired of it. i bit him just hard enough to make him whimper and asked if he liked it. he shook his no and has no bit me since.
i broke my daughter of screaming at me to ask questions by screaming at her when i answered her.
i broke her of pulling my hair by pulling her's.
all of these methods were used after i had exhausted the "NO! Don't bite Mommy." "NO! Don't pull mommy's hair." etc..... timeout, removing from situation....etc.... i even tried giving something acceptable to bite, something acceptable to pull, something acceptable to scream at.....
the kids are no worse for wear and are not any more inclined to violence than any child defending themselves.