When a cask or other structure containing air is tapped upon

When a cask or other structure containing air is tapped upon

When a cask or other structure containing air is tapped upon

In the examination of the chest we resort to percussion and auscultation. When a cask or other structure containing air is tapped upon, or percussed, a hollow sound is given forth. If the cask contains fluid, the sound is of a dull and of quite a different character. Similarly, the amount of air contained in the lungs can be estimated by tapping upon, or percussing, the walls of the chest. Percussion is practiced with the fingers alone or with the aid of a special percussion hammer and an object to strike upon known as a pleximeter. If the fingers are used, the middle finger of the left hand should be pressed firmly against the side of the horse and should be struck with the ends of the fingers of the right hand bent at a right angle so as to form a hammer. The percussion hammer sold by instrument makers is made of rubber or has a rubber tip, so that when the pleximeter, which is placed against the side, is struck the impact will not be accompanied by a noise. After experience in this method of examination one can determine with a considerable degree of accuracy whether the lung contains a normal amount of air or not. If, as in pneumonia, air has been displaced by inflammatory product occupying the air space, or if fluid collects in the lower part of the chest, the percussion sound becomes dull. If, as in emphysema, or in pneumothorax, there is an excess of air in the chest cavity, the percussion sound becomes abnormally loud and clear.