12 October

As a kid I used to see ‘pasteurised’ written on milk cartons and wonder what it meant. Louis Pasteur’s story is amazing, he came at a time when society debated whether life was something that was added to a broth in a flask by a vital force - the vitalists like Pouchet - or whether it was just a unique combination of chemicals - chemists like Liebig. Pasteur said, it’s neither. It’s microbes, a whole new type of being. This swan-neck flask was key to the spectacular experiments he did to convince people that microbes existed. The ‘swan’ neck prevents microbes from easily entering the liquid in the flask, so left alone a broth in a flask like this doesn’t go cloudy. But with a straight-neck flask, it does, because the microbes can more easily access the liquid. The rest is history, literally. Germs became new beings we had to take into account.