Then disproving causation. A fascinating use of Mammoth Cave in its history was a "good air" study on tuberculosis patients, because caves have great, naturally tempered air. That airflow is also tightly enclosed and many tourists and the doctors themselves caught the disease. It was a terrible way to help prove germ theory, but at the same time its hard not to blame them for trying because it was such a serious disease and anything to help was more than they had.