DECLINE OF THE SYSTEM. 621 



being also impaired, the muscles act more tardily 

 as well as more feebly, and the limbs no longer 

 retain the elastic spring of youth. The bones 

 themselves grow harder and more brittle ; and 

 the cartilages, the tendons, the serous mem- 

 branes, and the coats of the blood-vessels, ac- 

 quire incrustations of ossific matter, w hich inter- 

 fere with their uses. Thus are all the progres- 

 sive modifications of structure tending, slowly 

 but inevitably, to disqualify the organs for the 

 due performance of their functions. 



Among the most important of the internal 

 changes consequent on the progress of age are 

 those which take place in the vascular system. 

 A large proportion of the numerous arteries, 

 which were in full activity during the building 

 of the fabric, being now no longer w anted, are 

 thrown, as it were, out of employment ; they, in 

 consequence, contract, and becoming impervious, 

 gradually disappear. The parts of the body, no 

 longer yielding to the power applied to extend 

 them, oppose a gradually increasing resistance 

 to the propelling force of the heart ; while, at 

 the same time, this force, in common with all the 

 others, is slowly diminishing. Thus do the vital 

 powers become less equal to the demands made 

 upon them ; the waste of the body exceeds the 

 supply, and a diminution of energy becomes 

 apparent in every function. 



Such are the insensible gradations by which, 



