George never did any immunology on his own. He did have people, like me and others later, who did immunological experiments within his group. And what I was doing was- I can't really remember what was so special about that time. I think, perhaps, the most important single thing was showing that when you transferred immunity by these minces of cells, that immunity lasted forever. So it couldn't be, or would be extremely unlikely to be, any molecule. It had to be something- the cells themselves had to be surviving. And I think we went some way to proving that, did we? I'm not quite sure.