CHAPTER IX. 



THE CELL. DOCTRINE OF PHYSIOLOGY. 



REFERENCE has already been made at page 107 to the cause 

 of vitality ; alluding to it as a peculiar property impressed by 

 the Creator on all organized structure, a property altogether 

 distinct from Volition and Sensation, which exclusively belong 

 to animals, and which point out the existence of a special 

 entity, or being, resident in the organism, but whose properties 

 cannot properly be referred either to matter or its organization. 



Respecting the essential nature of the vital principle, much 

 speculation has been uselessly employed. Some have con- 

 founded it with the entity, or being, in the animal, which 

 perceives and wills. But this is manifestly an error, inasmuch 

 as it pertains also to vegetables. Very many parts of the 

 organization, also, have an independent vitality (without special 

 sensibility), separate from that of other parts, as we shall see 

 in the progress of this chapter. It seems, therefore, most rea- 

 sonable to define it as a peculiar property of organization ; as 

 gravitation, electricity, &c., are special properties of matter 

 under other circumstances, the essential nature of which are 

 just as mysterious as that of Life. 



Mysterious as this subject is, it is nevertheless interesting to 

 trace the origin and development of organized structures ; and 

 the progress of modern science has supplied us with the means 

 of instruction. Chemistry teaches us that the ultimate elements 



