DISEASES OF THE EESriRATORY ORGANS. 591 



smaller tubes have been rendered impervious, or that effusion 

 has taken place into the cavity of the thorax. 



Consolidation of the lung tissue, and the presence of fluid in 

 the thoracic cavity, can be recognised the one from the other — ■ 

 (1.) By the previous character of the sounds ; and (2.) By the 

 manner in which the absence is marked. In hydrothorax the 

 termination of the area of absence of sound is sharply defined 

 superiorly ; above the " water line " the pulmonary sounds 

 are generally exaggerated. In consoUdation the area of absence 

 of sound has no sharply defined limit ; at the lower parts of 

 the chest, and for some inches upwards, there may be no sound at 

 all ; then faint tubal sounds are heard, which increase in intensity 

 as the ear is moved upwards along the thoracic walls. Now 

 and then a blowing sound is heard in consolidation of the lungs, 

 confined as it were to the superficies of the lung, indicating 

 hepatization of the deeper-seated portions of the organ, leaving 

 the subpleural parts still pervious. ]\Iy experience leads me to 

 the conclusion that this superficial blowing sound is a bad 

 symptom, indicating a creeping pneumonic inflammation, having 

 a tendency to a fatal issue. 



4. Secondary crepitations. — Consolidation, as above described, 

 is succeeded by the breaking up and absorption of the exudate. 

 This process is marked by the advent of crepitations of a 

 bubbling nature, slowly evolved, few in number, dissimilar and 

 irregular in occurrence, more audible during insjoiration than 

 during expiration ; they mark the resolution of pneumonia, and 

 are succeeded by the natural sounds more or less modified. Such 

 are, then, the sounds of pneumonia. They are subject to modi- 

 fications, and to be variously mixed one with the other during 

 the various phases of the disease. 



PLEURAL SOUNDS. 



1. Friction soiincl. — A grazing, rubbing, grating, creaking, 

 irregularly jerking, superficial noise, heard more particularly in 

 inspiration, or in both respiratory acts. It results from the 

 rubbing together of the two opposed surfaces of the pleura, chiefly 

 heard at the lower part of the chest, where the pulmonary organs 

 have the greatest freedom, and is indicative of dryness of the 

 serous surfaces, or any cause of roughness upon them. This 

 sound is succeeded, when hydrothorax occurs, by — 



