90 PRACTICAL PHYSIOLOGY 



The movement of the upper ribs is chiefly forwards, and that of the 

 lower ribs backwards. The elasticity of the costal cartilages and the 

 sterno-clavicular articulations permit this movement. The bulk of 

 the lungs below lies behind and above in front. 



The thorax expands when the pleural cavity is opened in the corpse, 

 for the elasticity of the lungs pulls the thoracic walls inwards. In 

 quiet inspiration, therefore, the muscles have only to overcome the 

 elasticity of the lungs, and help the thoracic cage to spring outwards. 

 Expiration is brought about by the elastic recoil of the lungs 

 and abdominal wall, and by the weight of the thorax. 



Extraordinary Respiration. Let the subject run up and down 

 stairs until dyspnoea results. Every muscle is brought into play 

 which elevates the ribs, or fixes the origin of the muscles which 

 elevate the ribs. In expiration the abdominal muscles depress the 

 thorax and force up the dome of the diaphragm. Owing to the torsion 

 of the thoracic cage an elastic recoil takes place both after inspiration 

 and expiration, and thus no time is lost. 



During severe muscular exercise the abdominal wall is tightened, 

 and the diaphragm, its descent being resisted, raises the thorax. 



Vocal fremitus. Place the flat of the hand on the chest and 

 tell the subject to say "ninety-nine." The vibration of the voice 

 vocal fremitus is propagated through the bronchi to the wall of 

 the chest. 



Percussion. Firmly place the index finger of the left hand on the 

 chest and strike it with the middle and ring fingers of the other hand. 

 The sound resonates over the lungs. It is dull when the thigh is 

 percussed, for there the vibrations are damped. Note the feeling of 

 resistance to percussion. Map out the areas of resonance. On the 

 right side the resonance stretches from the apex of the lung in the 

 supra-clavicular fossa to where the liver dulness begins at the 6th 

 rib. On the left it extends to the cardiac dulness at the 4th rib. 

 The cardiac dulness reaches from the mid-line to a line which is convex 

 outwards, and runs from the sternal end of the 4th costal cartilage 

 to the apex of the heart. The apex-beat of the heart is felt about 

 3J inches from the mid sternal line, and in the fourth or fifth inter- 

 costal space. It shifts to the right or left as the subject rolls over on 

 to the right or left side. 



In the axillary line the pulmonary resonance extends to the 8-9 rib, 

 while behind it reaches to the 10-11 rib. Over the scapula the note is 

 less resonant. 



Observe the influence of inspiration and expiration upon the limits 

 of pulmonary resonance. 





