Hansen set himself the task of studying the properties of the varieties of yeast, and to do this he had to cultivate each variety in a pure state.
Duclaux stated that the yeast question as regards low fermentation has been solved by Hansen's investigations.
In the United Kingdom the employment of brewery yeasts selected from a single cell has not come into general use; it may probably be accounted for in a great measure by conservatism and the wrong application of Hansen's theories.
Hansen counted the number of yeast cells suspended in a drop of liquid diluted with sterilized water.
Hansen pointed out that this was by no means the case, for it is more difficult to separate the cells from each other in the gelatin than in the liquid.