In 1951 I attended the 2nd International Biochemistry Congress in Paris and presented my results there, and, after the meeting, a young Englishman called PG Walker came and explained to me that he'd obtained very similar results with another enzyme called beta glucuronidase, and so we discussed and felt that perhaps it would be interesting to compare the two enzymes, and it was a question of whether it would be done... the work would be done in his lab or in my lab. Finally we ended up agreeing that the work would be done in Louvain and he would provide some technical advice as to how to assay beta glucuronidase – again this was pre-Sigma days. And by that time I... my lab had begun to be a little known and a young man had joined us from Montreal, Robert Gianetto, a French Canadian, and I never knew whether he wanted to work with me or whether he wanted to race pigeons, because Belgium was very well known as a pigeon racing centre and he was, well, an ardent enthusiastic pigeon racer. Anyway, he was put on the problem, and with the advice of PG Walker, he worked out the technique for assaying beta glucuronidase and, as I said, this was again pre-Sigma days, so actually the technique was to take rabbits and inject them with phenolphthalein. Phenolphthalein is a dye that becomes red in alkaline medium and is used for crude pH measurements; it's colourless at the neutral pH and becomes red in an alkaline medium.