[MUSIC] They were trying to get this resistant mutants of the bacteria. And since they were thinking in quantitative terms, they wanted to get some ideas about what number of mutant would they get, what kind of number. And it was never reproducible. Sometime they would get a lot, sometime they will get few. Probably many other scientists would have seen that and ignored it. Luria didn't, and Max thought, the system is not just practical, and ignored it. So Luria continued to think about it. And he got a position as an assistant professor in Indiana. Delbrück, at that time, was at Vanderbilt in Nashville, Tennessee. And, Luria went to India. And you'd have to imagine this young, Italian man, introvert, uncomfortable in society, not drinking, not playing sports, arriving in a campus. And so his colleagues were very kind, so they decided to do what they would do for the new guy on the block. They took him to a bar for a Saturday night party. It sounds very nice, except he didn't dance, he didn't drink, he didn't speak all that well English. He was really lost. So he ended up on a chair next to the wall, and next to him was a slot machine. One of these machines where you put a dime, or maybe it was a nickel at the time, and sometimes you get another dime or sometimes you get more. You have to align the three different columns, and so on. The kind of machine you see in Las Vegas. So he sits there and he sees some of his colleagues playing with the machine and putting coins. And he tell them, you're stupid. You're bound to loose. And of course most of them lost, and weren't all that happy about this young Italian guy telling them that they were stupid. And then of a sudden, one guy hit the jackpot. Hit the jackpot means that he got several dollars out of a nickel or a dime. [SOUND], all the money coming down. The guy was happy, but Luria was even more happy. Because he thought, this is exactly what happens in my cultures. Sometimes there's a lot of mutant, I hit the jackpot. And sometimes they're very few, why, none. And I don't get anything. So that was December, 1943. That was January, 1943. So the first thing he does is to send a little postcard to Delbrück in Nashville, telling him his experiment and how this would apply to the result. So basically what Luria realized is that he was analyzing the number of mutants, and not the number of mutations. Because each mutation gave rise to a clone of mutants. If, in a culture that goes from 1, 2, 4, 8, 16, 32, 64, blah, blah, blah, a million cell. If the mutation occurs very early you get a big clone. If the mutation occurs very late you get a small clone. So on January 20th, 43, I thought that a clean cut experiment would be to find how fluctuation depends on the culture from which they come. If I find the number for resistance which fluctuate according to the Poisson law, If I plate ten samples of ten different cultures, all containing the same amount of bacteria, I find much larger variation. If the resistant are produced on the plate, they should show the same fluctuation in both cases. Now that's January 20th. Now remember there were no email. Phones were not very easy, telegrams were costly. So he sent a postcard on the 21st of January. Delbrück sends a postcard back. You are right about the difference in fluctuation of resistance when plating samples from one or from several cultures. In the latter case, the number of clones has a Poisson distribution. I think what this problem needs is a worked out and written down theory, and I have begun doing so. We are January 24th. February 3rd, the manuscript with the theory arrived, and Luria began experiments in that using the fluctuation. Now this is God damn fast. This is the kind of speed at which Delbrück could work. The paper would be sent in May and published in November issue of Genetics that same year. Now, Luria considered this paper to be really important, because it was a founding paper for material genetics. Delbrück had a very contrasting opinion. He considered this paper as a side issue which is threatening to displace the main issue by virtue of its explosive content of possibilities for studying bacterial genetics. The main issue is replication of virus. Bacterial variants have nothing to do with the replication of virus. Max was a physicist having fun doing biology. He absolutely hated being sidetracked to something that was not the issue of the time. His issue was the phage development. And for him this paper was an interesting paper. He didn't mind it, but it was certainly not central to the flow of ideas of the time. Which is quite amazing if you think of it.