Of Vegetation. 337 



Vcficles arc always dry ; in which ftate we 

 may plainly obferve every vcficle to be con- 

 trailed at each end by a Diaphragm or Sphin- 

 cter, whereby its too great lateral dilatation 

 isprevented, but not its diftenfion lengthwife. 



And as this pith in the quill grows dry 

 and fcfelefs after the quill is full grown, 

 we may obferve the fame in the pith of trees, 

 which is always fucculent and full of moifture 

 while the (hoot is growing, by the expanfion 

 of whic h the tender du&ile (hoot is diftended 

 in every part, its fibres being at the fame time 

 kept fupple by this moifture 5 but when 

 each year's (hoot is full grown, then the pith 

 gradually drys up, and continues for the 

 future dry and kikfey, its veficles being ever 

 after empty 5 nature always carefully pro- 

 viding for the fucceeding year's growth by 

 preferving a tender du&iie part in the bud 

 replete with fuceulent pith. 



And as in vegetables* fo doubtlefs in ani- 

 mals, the tender ductile bones of young 

 animals are gradually increafed in every part, 

 that is not hardened and offified 5 but fince 

 it was inconfiftent with the motion of the 

 joynts to have the ends of the bones foft 

 and duftile as in vegetables 5 therefore na- 

 Z turs 



