With the plan to research the chemistry of individual, simple cells, Friedrich Miescher dedicated himself to the leucocytes, the white blood cells, starting in autumn 1868 in the castle laboratory. In order to obtain leucocytes, he chose a less appetizing, but very productive source: He collected used bandages in the Tübingen hospital, so as to wash out the white blood cells contained in the puss.
At the beginning of 1869, following extensive examinations, he came across a completely new substance. Miescher named the substance “nucleic” (pronunciation: nu-cle-ic) – after the Latin word for core, nucleus. In order to examine the nucleus substance more thoroughly, Miescher applied the digestion enzyme pepsin which he won out of pig stomachs. With the help of the enzyme, the protein of the puss cells could be decomposed completely so that the only thing left over was pure nucleic.