Nowadays in biology, the bone is characterised as tissue consisting of bone cells, protein fibres and mineral matter. In his notebook Bogdan Kajak described a bone more simply. He wrote that it was only a composition of mineral salts and organic compounds. He proved this experimentally by:
-incinerating the bone, so that he obtained its mineral compounds,
-putting the bone to a solution of vinegar, so the bone became more squashy.
Now pupils experiment with bones in middle school, not high school.
