Of course that is not what happened. I spent the next few days mulling over the concept behind the baby machine and what fundamental flaw I might be missing. For whatever reason, the experiment Cooper and I did in Copenhagen crossed my mind, and something just snapped. I finally realized what the experimental result was telling us; namely, the rate of 14C-thymidine incorporation during the division cycle. It can be understood by considerring the following simple facts with reference to that experiment. The first newborn cells to fall from the surface at the start of elution were progeny of the oldest cells in the culture at the time of pulse-labeling with 14C-thymidine.