356 RESPIRATION [CH. XXVI. 



the ribs, must act also as muscles of expiration, and therefore we must 

 conclude that the abdominal muscles are assisted in their action by 

 the interosseous part of the internal inter costals, the triangularis sterni, 

 the serratus posticus inferior, and quadratus lumlorum. When by 

 the efforts of the expiratory muscles, the chest has been squeezed to 

 less than its average size, it again, on relaxation of the muscles, 

 returns to the normal dimensions by virtue of its elasticity. The 

 construction of the chest-walls, therefore, admirably adapts them for 

 recoiling against and resisting undue contraction as well as undue 

 dilatation. 



Graphic Record of Respiratory Movements. 



Among numerous methods which have been described for record- 

 ing the respiratory movements the simplest in the case of the human 



FIQ. 290. Stethograph tracings from the human subject. Each upstroke is due to inspiration ; each 

 downstroke to expiration. The lowest line is a time-tracing marking half-seconds. 



subject, especially if he be a patient in bed, is to fasten a bandage 

 loosely round the chest. Between the bandage and the chest-wall a 

 flexible hollow rubber ball is placed. This ball communicates by a 

 rubber tube with a recording tambour. All such appliances are 



