47^ OFOLDAGE 



as hard as bones. This rigidity of the cartilages 

 renders the motion of the joints extremely dif- 

 ficult, and, at laft, deprives us of the ufe of our 

 members, and produces a total cefTition of exter- 

 nal movements. This is a fecond, and more 

 •marked caufe of death, becaufe it manifefts it- 

 felf by a laborious performance of the common 

 a<5tions of the body. 



The membranes likewife become hard and 

 dry, as we advance in years. Thofe, for ex- 

 ample, which furround the bones, foon lofe 

 their flexibility. At the age of 20, they are 

 incapable of farther extenfion. The mufcular 

 fibres fufFer a fimilar change, in proportion to 

 the time of life ; though, to the touch, they feem 

 to be fofter as age increafes. It is not the muf- 

 cles, however, but the fkin, that occafions this 

 perception. After the body is come to its full 

 growth, the fat increafes, and, by being inter- 

 pofed between the fibres of the mufclcs, and 

 between the fkin and the mufcles themfelves, 

 makes them feel fofter, when, in reality, their 

 denfity is greatly increafed. Of this fad we have 

 an inconteftible proof, by comparing the flefli 

 of young with that of old animals. In the for- 

 mer, it is tender and delicate ; but, in the latter, 

 it is dry, hard, and unfit for eating. 



The fkin always extends as the body increafes ; 

 but, when the body diminifhes, the flvin has not 

 elafticity enough to enable it to contrad: to its 

 former diraenfions : It, therefore, continues in 



wrinkles 



