220 NORMAL PERCUTORY CONDITIONS IN THE THORAX. 



thorax is at rest. Within these limits, represented by the triangle t t' t" 

 in Fig. 84, percussion yields the cardiac dulness ; that is, a flat per- 

 cussion-note is obtained here. 



In the larger triangle d d' d" a relatively thin layer of pulmonary 

 tissue separates the heart from the chest-wall, and a dull note is obtained 

 on percussion. Only outside this triangle is the so-called pulmonary 

 resonance obtained. On deeper inspiration the inner border of the left 

 lung passes completely over the heart, as far as the mediastinal insertion 

 (Fig. 34), and thus the flat percussion-note is confined to the small tri- 

 angle t i i'. On the other hand, during forced expiration the edge of the 

 lung recedes so far that the cardiac dulness embraces the space t e e'. 



VARIATIONS FROM THE NORMAL PERCUTORY CONDITIONS 



IN THE THORAX. 



The investigation of the normal percutory conditions and their pathological 

 variations is of the greatest importance for the physician. Suggestions of percus- 

 sion (also of the abdomen) are found as far back as Aretaeus (81 A. D.). The 

 real discoverer, however, is Auenbrugger (d. 1809), whose fundamental work was 

 elaborated especially by Piorry and Skoda; the latter developed the physical 

 theory of percussion (1839). 



Over the area of the lungs the otherwise clear, resonant percussion-note is 

 impaired when the lungs have to a greater or lesser extent lost their normal air- 

 content; an airless space of 4 sq. cm. on the outer surface of the lungs will yield 

 a dull note. The note is impaired also when the lung is compressed from without. 

 The percussion-note is louder or hyperresonant in lean individuals with thin chest- 

 walls, or after deep inspiration, or in the condition of permanent expansion that 

 occurs in emphysematous persons. 



It should also be noted whether the percussion-note is of high or of low pitch ; 

 this quality being dependent to a certain extent on the degree of tension in the 

 elastic pulmonary tissue, but especially on the tension of the thoracic wall. As 

 this tension is increased during inspiration, and diminished during expiration, 

 there should be recognized a corresponding difference in the pitch of the note. 

 Deepest inspiration produces a higher pitch, on account of the increased tension 

 of the chest-wall and the lungs ; but at the same time the note diminishes in dura- 

 tion and intensity, as the more highly stretched parts possess a diminished ampli- 

 tude of vibration. Sometimes in the terminal phase of the deepest possible in- 

 spiration there occurs still another change in the percussion-note, in that there is 

 produced, a certain restoration of the depth and intensity, falling short, however, 

 of the original volume. During complete expiration the intensity is lessened and 

 the pitch lowered. 



Percussion of the larynx and the trachea yields a clear tympanitic note, whose 

 pitch depends upon the size of the cavity. The note is highest when the mouth 

 and the nose are open, or when the tongue is protruded, or when straining efforts 

 are made with closed glottis; it becomes lower when the head is extended back- 

 ward, or during the act of swallowing, as well as during intonation. It is higher 

 at the end of deep inspiration than during expiration. Affections of the lungs 

 that lessen the normal tension lower the pitch of the note. 



When the percussion-note partakes of a drum-like character, approaching a 

 musical sound, with distinguishable high and low pitch, it is termed tympanitic. 

 If a hollow rubber ball applied to the ear be tapped with the finger, a typical 

 tympanitic sound will result, the pitch of which is higher the smaller the diameter 

 of the ball. Tapping the trachea in the neck will also yield a tympanitic note. 

 The tympanitic note consists of a primary tone, together with several harmonic 

 overtones, arising from an air-space surrounded by relaxed and movable walls (the 

 non-tympanitic tone consists of the membrane-tone of a tightly stretched wall). 

 The tympanitic note in the chest is always of pathological origin. It is found 

 in the presence of a cavity within the lung-substance (when the mouth is closed, 

 and especially when the nose is closed at the same time, the note becomes deeper), 

 also in the presence of air in a pleural cavity, as well as in association with dimin- 

 ished tension of the pulmonary tissue. The tympanitic note is closely allied to 

 metallic tinkling, which arises in large, pathological, pulmonary cavities, as well 



