262 EXPANSIBILITY. 



If I proceed from flexible and elastic bodies, 

 to consider the attributes of those which are 

 essentially expansible, although they possess, in 

 common with the former, the capacity to be 

 bent into different forms, aqd even to be com- 

 pressed from a larger to a smaller volume, by 

 the agency of an external force ; they neverthe- 

 less, differ from both in points the most essen- 

 tial. Instead of requiring the agency of exter- 

 nal pressure, in order that they may be enabled 

 to unbend and expand, external pressure alone 

 is the means by which this expansive power is 

 bounded and confined; instead of being like 

 flexible and elastic bodies, naturally passive 

 and artificially active, they are naturally active 

 and artificially inert ; they are made flexible by 

 pressure, but are expansible without it. The 

 instant external pressure is removed, this ex- 



food undergoes, not only with respect to quantity but to qua- 

 lity also, not only with respect to configuration in general, but 

 to essential properties in particular, by the digestive and assi- 

 similating organs, with which animals and vegetables are en- 

 dowed. Having detailed at considerable length the nature 

 and relation which subsist between capacity and power in my 

 system of physiology ; to that work, I must refer the reader, 

 if he be desirous to understand the nature arid power of life 

 in converting the capacity of matter from a dead to a living 

 state, from a state of dispersion to a state of combination, 

 from a multitude of parts into one organised system, endowed 

 with animation and action. 



