PRACTICAL CONSIDERATIONS : THE LUNGS AND PLEURA. 1865 



over the sides and front, and it has been suggested that this is due to contact between 

 a bronchus and a rib, the latter conveying the breath-sounds directly to the ear. 



If the larynx or trachea is narrowed, the air has to pass through a constricted 

 aperture, must do so at a greater rate, and will make a louder noise, stridor. 



Rales are caused by changes in the mucous and epithelial lining and contents 

 of the air-passages. Like the normal breath-sounds, they are louder and noisier the 

 nearer they are to the larynx or the larger the tubes in which they are produced. 



Mucous rales are moist, are thought to be produced by the bursting of air- 

 bubbles in viscid or watery mucus occupying the larger air-passages, as in bronchitis, 

 and vary in character (i.e., in fineness or coarseness, or in loudness) in accordance 

 with the size of the tube that they occupy. The bubbling of air through the ac- 

 cumulating mucus in the larynx, trachea, and bronchi of a moribund person the 

 " death-rattle" is an example of the larger kind of mucous rales. 



Crepitant rdles are dry rales, due, it is thought, to the gluing together of the 

 opposing surfaces of a number of air-vesicles by an exudate, the entrance of air on 

 inspiration then causing a fine crackling sound, "like that which is heard when a 

 small bunch of hair near the ear is rolled backward and forward between the tips of 

 the finger and thumb" (Owen). If a similar condition affects the lumen of a tube, 

 if may produce larger rales, still dry, known as rhonchi (snoring) or sibili (hissing). 

 Other factors enter into the production of rales, but the chief underlying anatom- 

 ical conditions have been mentioned. 



Air entering a cavity {pulmonary vomicce, bronchiectasis*) causes a sound re- 

 sembling that produced by blowing into an empty bottle, amphoric. A peculiar 

 sound heard often in pneumothorax, and caused by the air from the fistulous com- 

 munication with the lung entering the pleural cavity and producing a bubbling 

 sound at the orifice, is described as metallic tinkling . It is also thought to be clue to 

 the dropping of liquid into an accumulation of fluid at the base of the pneumo- 

 thorax. 



Voice -soimds, like breath-sounds, are louder over the laryngeal, tracheal, and 

 bronchial regions. When the voice seems very close and loud to the ear placed 

 over other regions (pectoriloquy, bronchophony}, it indicates increased power of 

 conduction, i.e. , consolidation of lung-tissue. 



If the tremor from the vibration of the vocal cords in speaking (vocal fremitus) 

 is transmitted with increased distinctness to the hands placed on the surface of the 

 thorax, it has the same significance. If it is absent, it usually indicates the interpo- 

 sition of some relatively non-conducting substance, as air {pneumothorax}, or pus 

 (empyemei), or blood {htemothorax} . 



'Percussion-sounds vary with the region and the condition of the lungs and 

 pleurae. Normally, during quiet breathing, the resonance is increasingly clear from 

 the supraclavicular region downward over the front of the chest to about the fifth 

 rib on the right side where the pulmonary tissue begins to decrease in thickness on 

 account of the presence of the liver and to the sixth rib on the left side. It is less 

 above the clavicle and over it, on account of the comparatively small amount of lung- 

 tissue in the apices ; and over the upper part of the back, on account of the interpo- 

 sition of the scapulas and of thick muscular masses. It becomes diminished in the 

 presence of moderate effusion, as in oedema ; dull if there is consolidation of lung- 

 tissue ; and is absent (flat) if there is either plastic exudate or fluid effusion in the 

 pleural cavity. In pneumothorax, or over a cavity in the pulmonary tissue, especially 

 if it is superficial, the percussion-note is tympanitic. 



Injuries. Contusions of the lung may occur without fracture of the bones of 

 the thorax or obvious lesion of the parietes. They are thought to be due to 

 suddenly applied elastic compression when the glottis being closed the lung or 

 the lung and pleura are ruptured as one may burst an inflated paper bag between the 

 hands. 



The consequences are interlobular emphysema, the air having escaped from 

 the ruptured air-cells into the connective-tissue spaces of the lung (vide infra); 

 general emphysema, the air reaching the subcutaneous cellular tissue of the neck and 

 trunk through a ruptured pleura, or, the pleura being unbroken, passing from the 

 root of the lung into the mediastinum and thence to the base of the neck; pneumo- 



