OF MOVEMENTS OF CHEST-WALL IN RESPIRATION. 261 



the course of the inspiratory and expiratory tracings ; and, 

 second, in the form of the cough-movements, the closure 

 of the glottis taking place after some degree of expiration 

 had been accomplished. 



Figs. 12 and 13 display the movements of the third ribs 



in a healthy female, a3t. 29 years. The pliability of the 

 bones is well shown both by the large extent of forward 

 movement in proportion to the upward rise, and by the 

 variations in the curves of inspiration and expiration. 



In the boy, set. 11, from whom the tracings given in 

 figs. 14 and 15 are taken, the same elasticity is apparent, 



and the curves also demonstrate the great freedom of 

 movement possessed by the thoracic walls in childhood. 



Figs. 16 and 17 mark the differences in the healthy 

 tracing produced by advancing years. There is an ap- 

 proach to the form of curve traced by the unyielding rib ; 



