 He was not very interested in this however, and he increasingly spent his free time at the Berlin Zoo sketching and studying the animals there.Zoo animals were not subjects he could handle physically; he could not get under their skin and see for himself how muscle, bone, tendon and tissue melded together to form the living animal.In order to get a better look at the anatomy of animals, Rungius made frequent visits to the local glue factory to study animal anatomy in its most basic form.