"Proven."

William H. Dudley
1907 Journal of the American Medical Association (JAMA)  
Percussion of the chest by ordinary methods is at best unsatisfactory; and, as practiced by many physicians, is unreliable and worthless. During recent years I have acquainted myself with most of the different varieties of percussion and have compared my findings by one with that of the others. I find that the various methods have different value under differ¬ ent circumstances. By being conversant with more than one method one is able to do more accurate work.
doi:10.1001/jama.1907.02520490047015 fatcat:qwxmgxqzgrfjpn6w432qly7i24