I failed to mention earlier something that I regret having overlooked and that is that one of the main issues in respect of the research that I had planned was to make sure that the cells that I obtained from these foetal sources were normal. By this time, as I think I mentioned earlier, it was known that the 46 chromosomes is the true number of chromosomes for humans. And, of course, many people in the institute knew about my work as I knew about their work. We often met and discussed activities and because I... one of the variables that had to be determined in order to prove that my cells were normal was their what's called 'cariology', which means their chromosome number, not only the number of chromosomes, but the shapes of the chromosomes, how they look. At that time, that was critical in saying that... that a cell was normal. So I asked Paul Moorhead, my good friend at the Wistar Institute, to help me in establishing that these cells were normal in respect of their cariology, their chromosomal configuration and Paul happily did that for me. And he did that study for every cell strain that I subsequently worked with and I'll return to that issue later. But Paul was a very significant personality in this story. I had frequent conversations with him. He was a very bright man. And in fact, he suggested several experiments that were very critical and I'll discuss these subsequently.