Outline of Lung 191 



Pneumothorax. When the pleura is full of air (p. 187) the percus- 

 sion note is tympanitic, but as more air is pumped in at each expira- 

 tory movement the tension becomes so great that the air can no 

 longer vibrate and the sound becomes metallic. These sounds may be 

 imitated by slightly blowing out the cheeks and sharply striking one 

 of them with the finger-nail, and then again striking when they are dis- 

 tended to the utmost ; in the latter case the note is more metallic. 



The most likely cause of pneumothorax is the opening up of a 

 vomica, but this is often provided against by the concomitant pleurisy 

 having glued together the visceral and parietal layers. Malignant 

 ulceration of the oesophagus sometimes lets air into the pleura, and 

 the same condition has followed a mediastinal emphysema which was 

 secondary to tracheotomy. (Fagge.) 



In pneumothorax there is, as a rule, a certain amount of fluid in 

 the cavity as well as air (Jiydro-pneumothorax), and in either of these 

 conditions, the pleura being distended, the apex-beat may be displaced 

 right or left, as described in hydrothorax (p. 189). 



THE LUNGS 



In infancy the colour of the lungs is pinkish ; in adult life grey, 

 from the presence of particles of carbon ; and in those who have worked 

 in coal-mines it may be quite black (anthracosis). 



The lung-tissue of the foetus, and of the newly-born child, unless 

 breathing has been instituted, is solid and sinks in water, but after 

 respiration it has become buoyant ; in this way it is determined whether 

 an infant found dead was still-born or not. Pieces of the lung from 

 which air has been dispelled by pneumonic exudation also sink in 

 water. 



The apex of the lung mounts in the robust an inch and a-half 

 above the first rib, or an inch above the clavicle, into the region cor- 

 responding to the triangular interval between the posterior border of 

 the sterno-mastoid and the anterior border of the trapezius. The sub- 

 clavian artery grooves the front about in. below the very apex, being 

 separated from the lung by the parietal pleura. (See fig. on p. 164 ) 



The bases of the lungs reach much lower behind than in front, for 

 in front the diaphragm is level with the sterno-xiphoid joint. They are 

 concave, corresponding with the surface of diaphragm, and are de- 

 limited by an oblique line passing over the chest from the sterno- 

 xiphoid joint over the costal cartilages and above the last rib, and to 

 the spine. The base of the right lung is immediately above the liver, 

 the limit of its resonance and of hepatic dulness being clear and 

 definite. The base of the left is above the stomach, and it is generally 

 easy to define the area of the pulmonary resonance from the metallic 

 note of the stomach. Still, the student must guard against mis- 



