184 DISEASES OF THE PARENCHYMA OF THE LUXG. 



The morbid intensity of the pectoral fremitus, during the stage of en- 

 gorgement, depends upon the loss of elasticity which the pulmonary 

 tissue sustains at this period. Under normal conditions, the transmis- 

 sion of the vibrations from the trachea and larger bronchi to the thoracic 

 wall is impeded by the tension of the elastic vesicles ; moreover, the 

 elasticity of the healthy lung exerts a sort of suction upon the inner 

 surface of the thorax, whereby thoracic vibrations are held in check. 

 These two forces, by which the normal vocal resonance is enfeebled 

 during health, are removed when the elasticity of the lung is destroyed. 

 The still further increase of the vocal fremitus, which is often observed 

 during the stage of hepatization, is owing not only to the loss of elas- 

 ticity of the hepatized lung, but also to the fact that the vibrations 

 which the vocal chords have imparted to the air within the trachea and 

 bronchi pass unimpaired to the walls of the chest, as the medium 

 through which they are transmitted is no longer an interrupted one 

 (alternations of air and vesicular wall), but a continuous one, the solidi- 

 fied pulmonary parenchyma. It sometimes happens that the trans- 

 mission of the vibratile waves is checked by a temporary occlusion of 

 the bronchi by secretion ; but we not unfrequently observe instances, 

 hi which the pectoral fremitus over a hepatized point is permanently 

 weakened or is entirely deadened, when there is neither bronchial 

 obstruction nor pleuritic exudation. In such cases we may infer that 

 the close contact of a compactly-infiltrated lung prevents the walls of 

 the chest from vibrating. 



Percussion during the stage of engorgement often gives rise to a 

 purely tympanitic, hollow sound. The elasticity of the normal lung 

 may be compared to that of a tightly-inflated bladder ; its ring is not 

 tympanitic. In the stage of hepatization the vesicles having lost their 

 elasticity, its condition is like that of a cluster of imperfectly-inflated 

 bladders. Its percussion-sound then is tympanitic. The "hollow" 

 percussion-sound depends upon a diminution which the exudation 

 causes in the amount of air contained in the vesicles, thereby reducing 

 the size of the vibrating body. We regard the expressions "full " and 

 M hollow " as thoroughly intelligible and practical By universal cus- 

 tom, the sound produced by the vibration of a large voluminous body 

 is called a " full " tone, and that proceeding from the vibration of a 

 small body is called a " hollow " tone. Thus, the percussion-sound of 

 the stomach sounds full to the ear of the beginner ; that of the small 

 intestine hollow. I find that there are few practitioners who can recog- 

 nize with facility that the tympanitic percussion-sound of engorgement 

 also is hollow, while for many it is difficult to make out its higher 

 pitch. 



During hepatization, when the solidified point lies in immediate 



