i;8 



LIMITS OF THE LUNGS. 



regions, during expiration, the surfaces of the visceral and parietal pleurae are in 

 contact, but during inspiration they are separated, and allow the thin margins of 

 the lung to be insinuated between them. This available space is called comple- 

 mental space (Gerhardt), or "disposable" or reserve-pleural space by Luschka 

 (EickhoKst).] 



It is important to observe the relation of the margin of the left lung to the heart. 

 In fig. 142 a somewhat triangular space, reaching from the middle of the point of 

 insertion of the fourth rib to the sixth rib on the left side of the sternum, is 

 indicated. In the passive chest, the heart lies in contact with the thoracic wall in 

 this triangular area ( 56). This area is represented by the triangle t, t', t", and 

 percussion over it gives a dull sound (superficial dulness). 



In the area of the larger triangle, d, d\ d", where the heart is separated from the 

 chest-wall by the thin anterior margins of the lung, percussion gives a muffled sound, 

 while further outwards a clear lung percussion-sound is obtained. During deep 

 inspiration, the inner margin of the left lung reaches over the heart as far as the 



Fig. 142 

 Topography of the lungs and heart, h, I, upward limit of margin of lung during deepest expira- 

 tion ; m, n, lower limit during deepest inspiration ; t, t', t", triangular area where the 

 heart is uncovered by lung, dull percussion-sound ; d, d\ d", muffled percussion-sound ; i, 

 i', anterior margin of left lung reaches this line during deep inspiration, and during deep 

 expiration it recedes as far as e, e'. 



insertion of the mediastinum, whereby the dull sound is limited to the smallest 

 triangle, t, i, i. Conversely, during very complete expiration, the margin of the 

 lung recedes so far that the cardiac dulness embraces the space, t, e, e. 



115. PATHOLOGICAL PEECUSSION-SOUNDS. Abnormal Dulness. The normal clear re- 

 sonant percussion-sound of the lungs becomes muffled when infiltration takes place into the 

 lungs, so as to diminish the normal amount of air within them, or when the lungs are com- 

 pressed from without, e.g., by effusion of fluid into the pleura. The percussion-sound becomes 

 clearer when the chest-wall is very thin, as in spare individuals, during very deep inspiration, 



