Bubbling, clicking, crunching, knocking and tapping sounds emanating from the chest are rarely encountered in civilian practice and their significance is not generally appreciated. With the current great military mobilization physicians will undoubtedly encounter these sounds in many instances of thoracic wounds in military personnel and in civilians. It appears pertinent, therefore, to emphasize their mechanism of production and their diagnostic significance.
Tapping, clicking and snapping metallic sounds were encountered by Rees and Hughes1 and Smith2 in soldiers with wounds of the left side of the chest during the last war. These sounds varied in intensity from ones audible only with the stethoscope applied over the precordium to those which could be heard 6 to 8 feet (183 to 244 cm.) from the patient. They were synchronous with the heart beat but varied in relation to the cardiac cycle. Some were audible only during systole, others only during