So here was a new phenomenon. They called it immunological tolerance and made a theory how it could arise and so on. Well then Hašek realized that what he saw was the same thing. That actually because in the early stage of development when the immune system is maturing it learns to tolerate foreign cells and antigens. So if the blood circulated between the two embryos the chicken considered the foreign blood as their own. So they were actually chimeras. They had two kinds of blood cells. So it was not that they inherited new antigens. They just had blood cells of the other embryo... of the other... yes, embryo that they tolerated. And they exchanged skin grafts between the chickens. The skin grafts were accepted just like in the mouse case. So they realized that they discovered immunological tolerance, Hašek did. Both Medawar and Hašek did it in 1953. They published it in the same year. Medawar, as I said, in Nature, Hašek in Čsl. biologie... or Folia biologica... or something - a journal that was virtually unknown. Now, Medawar got a Nobel prize for it. Hašek got nothing. Whether it was fair I don't know. He discovered the phenomenon. He didn't know what it meant. He put the wrong interpretation on it, but he did come to the same result as Medawar. Anyway Hašek was not terribly upset about it. He accepted it. He congratulated Medawar and said, 'You deserve it and it's okay. No problem'.

So that was the Hašek that turned from Lysenkoism to... from study of genetics to immunology. So at the time when I came to the institute it was all concentrated on immunological tolerance, the mechanism, and the conditions under which you can induce it, and so on and so forth. There was another group headed by Jan Svoboda who was working on tumor viruses, but that was it. What Hašek gave me I think was some kind of an attempt to save something from his Lysenkoist past, and again I have to digress a little bit. It was the time when there was fantastic development in microbial genetics with bacteria, with phages, with viruses. You could do so many things that you cannot do with large plants or animals. You could test millions of bacteria in a few hours. You cannot breed millions of mice in your lifetime. So... and there were many things that were discovered through microbial genetics, and now was the question, how to do it? How to do the same thing? The fine mapping of chromosomal... whole chromosomal regions like they did in bacteria. How to do it on eukaryotic organism, in animals and plants. And there were various attempts and one of them was... well, we cannot do it through the germ lines. We cannot breed mice in such large numbers. But we can do it maybe with cells. Not with germ line cells that produce sperm or eggs, but with somatic cells... any cell of the body. Let's see if we can hybridise instead of animals, if we can hybridise cells. And then you have millions of cells and you can work just like with bacteria with cells in a tissue culture. So... and it worked. You could fuse cells. Boris Ephrussi in Paris and Henry Harris in London showed that fusion of cells is possible and that segregation of the chromosomes in the hybrid does occur. So the basic principles of doing Mendelian genetics on simple and isolated cells was there.