OF VEGETABLE TISSUE. 23 



subject to the laws of physical and chemical 

 action ; we must therefore inquire, in the first 

 place, concerning every fact of their existence ; 

 whether it is merely a consequence of those laws, 

 or whether that consequence be modified by the 

 structure and condition of their organization. 

 The first case will come under the class of 

 simple chemical or physical facts ; the other will 

 range itself among those which are denominated 

 properties of tissue ; that is, properties which are 

 not indeed strictly vital, but which arise from the 

 peculiar structure of living bodies. Other facts, 

 which we cannot include under either of the 

 above heads, are the direct consequences of that 

 mysterious state called life. The distinction of 

 these three classes is the basis of all true physi- 

 ology. 



16. Vegetable tissue possesses three proper- 

 ties which deserve attention, viz. Extensibility ; 

 Elasticity ; and the power of imbibing moisture. 



17. Extensibility. All organic tissues have 

 in a greater or less degree the power of extend- 

 ing themselves even in the act of growth. This 

 property is greater in proportion as the tissue has 

 received fewer solid deposits, diminishes as it 

 becomes older, and at a certain period ceases 

 altogether. If we watch the development of a 



