590 SPORADIC DISEASES. 



excavations from tubercle, dilatation of bronchi, pus in pleura, 

 with a bronchial fistula and deliquescence of gangrenous lung 

 structure. 



rULMONArcY SOUNDS, 



1. Crepitations. — Crepitant rale or rhonchus ; compared to the 

 sound produced by rubbing slowly and firmly between the finger 

 and thumb a lock of one's hair near the ear, or to the crackUng 

 of salt when scattered over hot coals. It is heard during inspira- 

 tion only, and indicates the primary stage of pneumonia. " Pro- 

 bably due to the sudden expansion of delicate tissue, altered in 

 its physical properties by the inflammatory state, and whicli 

 probably undergoes minute ruptures." — (Aitkex.) Tliis sound 

 is best heard in the lower thh-d of the chest, replacing the vesi- 

 cular murmur. After continuing for a sliort period it may 

 disappear, and the vesicular murmur return, indicating tlie 

 resolution of the inflammation. Usually, however, the crepita- 

 tion becomes fainter and fainter, and is substituted by — 



2. Tiihal or Bronchial sound. — The tubal or bronchial sound, 

 when heard over the inferior portions of the thorax, indicates 

 some degree of consolidation or hepatization of the lung tissue. 

 It shows, in fact, that the minuter ramifications of the bronchi 

 and air vesicles have become impervious to air, by the pressure 

 of an exudate within and upon their walls, and that the larger 

 tubes of the part are still pervious. Ii; health, both vesicular 

 and tubal sounds are emitted b} all parts of the lung tissue, but 

 can be detected by auscultation in certain parts only. For 

 example, the tubal sound is so loud ii; the upper and anterior 

 parts of the chest, as to mask or hide tlie vesicular murmur to a 

 great extent ; and, conversely, the vesicular murmur being loudest 

 at the inferior portions, masks or renders inaudible the tubal or 

 bronchial sound. When, however, those portions of the lungs, 

 namely, tlie minute tubes and air vehicles, are rendered impervi- 

 ous — the larger sized tubes still remaining pervious — it naturally 

 follows tliat the sound emitted by air passing in and out of the 

 larger tubes now becomes audible. 



In many instances, however, the tubal sound continues for a 

 short time only, and is succeeded by — 



3. Absence of sound. — When this occurs it indicates that the 

 exudation is excessive in cLuantity, that the larger as weU as the 



