Does laughing gas really make you laugh?

My question is about blood. In my medical terminology class, we were told that you can distinguish an old internal bleed from a relatively fresh one by the colour of the blood: a fresh bleed produces bright red blood but an old bleed produces brown blood. I was curious as to what makes the blood turn brown.

I've always been thin and can eat and drink what I like. Why is this? Linda in Norwich - Why is it that people tend to increase weight when they get to middle age? Rob in Milton - Why do some people get fat and others don't?

I have a health question for you. If someone works out a lot and is in great physical shape but eats foods which are very high in fat or cholesterol, in what condition is his or her heart likely to be? Does the working out negate the bad diet or does it keep you looking good on the outside but on the inside you may have serious heart problems?