Richard (1945) described a method to test the cellulose and protein breakdown in the soil. He placed viscose and silk threads in the soil sometimes for more than one year and measured their tensile strength after removal from the soil. This method was used by Van Goor (1952) for forests soils in the Netherlands. He measured the tensile strength of rayoncord A U, a twisted cellulose thread, while Hueck (verbal information) measured the tensile strength of a cylindrical non twisted cellulose thread. Measuring the tensile strength has to be done under constant temperature and humidity and it is not easy to get reproducible results.