The degradation of the walls in the Mondmilch Gallery, between the Nave and the Chamber of the Felines, is the result of natural alteration mechanism that is most often linked to the presence of bacteria that modifies the structure of the calcite. Depending on its degree of humidity, the plasticity of the phenomenon changes from a chalky state to that of "fromage blanc", as André Glory used to call it sometimes. This is a phenomenon common to a number of caves.