Very stupid today. Inserted a mercury thermometer into my nearly 3 year old dd's mouth. She seems so grown up now, I didn't think it would be a bad idea. She promptly bit the end off - crunching glass between her teeth. It was awful. Now, having been to A&E, we understand that it is not dangerous to swallow small amounts of mercury and we are praying that the glass she swallowed will not do any internal damage. Just thought I'd warn any others out there...