OF THE CHEST 37 



so, to raise or to depress the ribs. Hence it is, 

 that both in inspiration and in expiration the 

 elasticity of the ribs is called into play; and, 

 were it within our province, it would be easy to 

 show, that the dead power of the cartilages of the 

 ribs preserves life by respiration, after the vital 

 muscular power would, without such assistance, be 

 too weak to continue life. 



It will at once be understood, from what has 

 now been explained, how, in age, violent exercise 

 or exertion is under restraint, in so far as it de- 

 pends on respiration. The elasticity of the car- 

 tilages is gone, the circle of the ribs is now un- 

 yielding, and will not allow that high breathing, 

 that sudden and great dilating and contracting 

 of the cavity of the chest, which is required for 

 circulating the blood through the lungs, and re- 

 lieving the heart amidst the more tumultuous 

 flowing of the blood which exercise and exertion 

 produce. 



