So I wrote to Carl Cori, and I still have his reply. By that time I could only spend six months away from... because I had started... I had been appointed in Louvain as a lecturer, and so he wrote and said, 'Sorry, but I can't take a fellow for more than... for less than one year, six months... so I can't take you. In addition, there is... with you, there is the additional difficulty that we do not see eye to eye, with respect to the mechanism of action of insulin.' So I was devastated and... but then a couple of months later I got another letter from Carl and he... the letter said, 'I want to get back to your request. Earl Sutherland in my laboratory has just found that the action of insulin on liver slices... the glycogenic action releasing glucose from glycogen is not due to insulin but to an impurity. I believe you have also done some work on this, and perhaps you might be interested in working with Dr. Sutherland.' Now, when he said, 'I believe you've already done some work', in fact, he was referring to what I would consider my first discovery. During the war, when I was writing this book and reading everything about insulin and trying to make sense of everything, I had run into a paper by a man called Bridge, published in 1938, in which he had truly found evidence that insulin would release glucose from liver glycogen. I won't go into the detail but the evidence was convincing. And so this worried me very much, because I said, 'Well, the evidence is there and I don't believe it is correct because I have other reasons to believe the opposite.' Fortunately, as I said, I had read a lot about insulin and in my reading I had read about an impurity that the early people who had started purifying insulin – in the United States, after it was discovered – had found as an impurity, and they had shown that this impurity could be removed when you crystallised insulin according to a rather complicated technique, developed by a man called Abel. And so crystalline insulin did not contain this hypoglycaemic impurity.