In order to keep my research activities in a proper temporal perspective, I need to make another aside and that is to discuss an entirely different research subject in which I was involved at about this time and it will become clear in a moment why it's important. The research activity has to do with my knowledge of the mycoplasmas that I described earlier that were the focus of my PhD dissertation because by this time in the early 1960s, it had been discovered that cell cultures in many labs were contaminated with these organisms. The questions were twofold, at least twofold. Where was this contamination coming from? These organisms are microscopic. They're the smallest free living organisms. Because they're free living, they can grow in the same media that you're using to culture your cells and you don't want them or anything else in there to confound your experiments. Secondly, how do you get rid of them?

Well, because I was maybe one of a half a dozen people in the United States at least and I think also in the UK there were a couple of people, who knew how to grow these animals. Many of my colleagues who knew about this and were working in cell culture – and by this time there were increasing numbers – would get in touch with me and say, 'Hey, Len, can you help me find out, I'm having trouble culturing my cells, can you help me find out whether they're contaminated with mycoplasmas.' There was no way I could say 'no', of course, and so one aside, I was culturing people's cell cultures, samples of which were sent to me, or brought to my lab, and I was probably testing three or four a week and then keeping records and sending the results so it occupied a substantial proportion of my time. But I was happy to do it because these were all friends of mine.