Y: (NOSE PLUGGED) Oh my gosh, Don! What is that smell?

D: It's rotting fish, course, Yael. You see, I'm conducting a little experiment. This hunk      of sirloin and this cod have been sitting around for three days, and still the sirloin      doesn't stink nearly as badly as the fish.

Y: (NOSE PLUGGED) Don, please, can we throw that stuff out? It's making me      woozy.

D: Okay, sure. But haven't you ever wondered why fish stinks so much more than meat?

Y: (NOSE PLUGGED) Um! no--(UNPLUGGED) oh, that's better--I haven't.

D: Well, it's because fish tissue contains an odorless chemical known as trimethylamine      oxide. Once the fish is killed and the fish's tissues are exposed to air, the bacteria in      the fish's body break down this chemical into two new chemicals that are derivatives      of ammonia, and therefore smell pretty bad.

Y: Downright noxious, I'd say. But I still don't get why that doesn't happen with meat.

D: The main reason is that regular meat doesn't contain high amounts of trimethylamine      oxide, and fish do. This chemical is especially common in the flesh of cold-water      surface-dwelling fish like cod. So cod would start smelling faster than, say, catfish.

Y: Well, I hope you don't plan to test that fact too.

D: Don't worry, Yael! I'll wait until you go home. Also, keep in mind that the extent to      which you hate the smell of fish is in part culturally determined. People who don't eat      fish find its smell a lot more offensive than people who eat a lot of it. Plus, because      we associate rotting fish with food poisoning, we're conditioned to find its smell bad      rather than appetizing.

Y: Oh, so it's my fault the fish smelled so bad?

D: Well, the nose of the beholder!  

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