At a convention of biological scientists, one researcher remarks to another, "Did you know that in our lab we have switched from mice to lawyers for our experiments?"
"Really?" the other replied, "Why did you switch?"
"Well, for five reasons. First, we found that lawyers are far more plentiful. Second, the lab assistants don't get so attached to them. Third, lawyers multiply faster in numbers. Fourth, animal rights groups will not object to their torture. And fifth, there are some things even a rat won't do. There is a drawback, however; sometimes it's very hard to extrapolate the test results to human beings."