118 



CLINICAL DIAGNOSTICS. 



and assumes a z^'histliiig or hissing character. If the sweUing 

 of the laryngeal mucous membrane is loose, or deposits of exu- 

 date cover the membrane, the sound produced is rattling or 

 purring. 



IX, Percussion of the Thorax. 



To properly percuss the lungs a knowledge of their topo- 

 graphical position is essential. 



Anatomy. The lungs and heart do not occupy the whole of 

 the thoracic space. The abdominal viscera encroach upon a 

 greater part of it. The partition between the chest and abdominal 

 organs is the diaphragm. This organ is inserted, in the arc of a 

 circle, to the inner surface of the whole thorax, reaching in an 



Fig. 32. 



Dorsal and ventral boundaries of the field of pulmonary percussion. — - — Costal 



attachment of diaphragm. H. heart, d. c. dorsal colon. 1. v. c. left ventral colon. 



oblique direction from the sternum backwardly and upwardly to 

 the lumbar vertebrae. In the region of the sternum its points of 

 attachment are at the union of the ribs to their cartilages, farther 

 posteriorly, howev*er, the diaphragm does not extend down as 

 far as th-^ cartilages of the false ribs, but passes obliquely across 

 their inner surfaces until, finally, at the last rib. it finds attach- 

 ment at the superior end. The diaphragm arches forward from 



