Since the Coleridge quote went over well the other day, I thought I'd return to the line above (from Hilare Belloc) to talk about why things advance slowly in the tox field. It's fear. Justifiable fear. When toxicologists find something that seems to work, they stick with it. They're not easily convinced by the latest gizmos. No one wants to be the first to rely on a new technique and have it backfire, because the consequences in patients are potentially so terrible.

Any new technology (gene chip assays, for example) has to piggyback on the existing stuff for a long time, until there are plenty of cases to show how well it correlates with the existing methods. Given the length of the drug development process, this is a matter of years, many years.

You also want to know when the new stuff might be likely to break down, so you know when to give less weight to the results. The worst thing you can have in a tox test is a false negative, because that can kill people. The second worse thing is a false positive, because that can kill drugs. There's not much room to fool around in.