"And what if we don't find the right conditions?" Brother Joseph asked, "We may not pick the right properties to test, after all, temperature is only one possibility. Also, we don't have much time. This is a research project that could last a year, with no guarantee that we might not still be searching for an answer a twelve-month from now, and we only have a few weeks. We need a rapid way of testing a lot of different conditions all at once."
"Yes," said Mendel, "you are right. The only way to approach this problem is systematically. All conditions and properties must be tested in a logical and defined order. We must guard against irrational thoughts and the temptation to test too many different properties all at once. If we skip here and there with no research plan, we could end up wasting our time. Scientific investigations must proceed in logical and sequential steps, each possibility tested in its turn." He looked round at the laboratory and sighed. "Unfortunately, this is what we have to work with." He waved his hand at the mess of bottles, liquids, ingredients and other items they had collected the previous day. "With what we have here, a year would be a short time to test all the many possible ways to kill the rods and help the yeast."
"What if we were to use smaller bottles, like the ones found in an apothecary's shop?" Klacel suggested, "We could then set up many more experiments and test many more possibilities all at the same time."
"That is a good idea," Mendel agreed, "but it would still be a lot of work, and where would we get the small flasks from? I don't think Abbot Napp would give us the money."
"Perhaps Herr Druer would fund our research, after all it is to his benefit."
"Only if we succeed."
"It would be so much easier if we could only separate and grow the rods and the yeast apart from each other," Brother Joseph added.
"I think I have a way of doing that," Brother Matthew said, after a moment's thought. "The yeast are easy, Herr Druer should be able to provide us with an uncontaminated sample from one of the vats that is not going sour."
"And the rods?"
"If we start with a very small amount of a heavily contaminated sample, where there are more rods than yeast, and place that sample into a large quantity of sterilized broth, the rods and yeast will be diluted out and will be separated away from each other. If we then take lots of small volumes of the dilute material and put them into separate bottles, the chances are we will have at least one bottle or flask in which we have put broth with only one rod and no yeast. As the rod grows, it will produce more rods, all descendants of that first rod we put into the small flask. It should be a pure sample."
Sensing that this was a good idea, Mendel quickly wrote it down on Abbot Napp's finest paper, and drew out a sketch of the principle Klacel had just outlined. He titled the idea, On using dilution to bring about the separation and purification of a mixed culture.
"I think it would work," Brother Joseph said, as he watched Mendel put pen to paper. "But we still have two problems, how do we get all the flasks or bottles we would need to make it work, and how do we know which flask contains only pure rods with no yeast?"