CHAP. XTV.] ORGANIC FUNCTIONS. 155 



was, on their obvious connexions. That which I am going 



to use is intended, on the contrary, to explain the way in 



which one function is developed out of another. The law 



of the development of organisms, as we have seen, is that 



they are developed out of simple germs, and that the parts 



are gradually differentiated the one from the other. The Develop- 



same is true of functions; — functions also are developed by functions 



gradual differentiation. I may not, perhaps, be able to g^^^^^^^' 



make this last statement perfectly intelligible, until I come 



to the subject of mental science ; it is, however, implied in 



the views I have to state in this chapter. 



We have seen that all organisms transform matter and Their clas- 

 energy. The transformation of matter is the peculiarly ^^^^ '^^^•g"^ 

 nutritive, or vegetative, function ; the transformation of t)asis. 

 energy is the peculiarly animal function, and is generally 

 motor — that is to say, the energy is generally transformed 

 into motion, though in particular cases it is transformed 

 into heat, electricity, or light. 



Let us speak of the vegetative functions first. The Vegetative 



. , . , . 1 functions 



primary vegetative function, which is the ground and con- chemical, 

 dition of all other vital functions whatever, is the decom- 

 position, by plants, of water and carbonic acid, and the 

 formation of organic compounds. This function is in its 

 results a purely chemical one, though it produces combina- 

 tions which, as I believe, no chemistry but that of tlie 

 living vegetable organism can possibly produce.^ The 

 power of decomposing carbonic acid, and probably of de- 

 composing water also, is peculiar to the vegetable king- 

 dom, though not universal in it.^ Animals cannot decom- 

 pose carbonic acid, and consequently cannot form the 

 primary, or first-formed, organic compounds for them- 

 selves ; but they effect various transformations in the 

 organic compounds which they receive in their vegetable 

 food. Some of these transformations may perhaps be due 

 to the ordinary chemical forces, acting as they might act in 

 a laboratory ; but some are certainly due to a peculiar vital 

 action, controlling the chemical forces. This is eminently 

 the case in secretion : one set of secreting cells separates 



1 p. 86. ^ See Note A at end of this chapter. 



