198 THE INDUCTIONS OF BIOLOGY. 



Moreover since each kind of protozoon, even the lowest, has 

 its specific mode of development and specific activity — even 

 down to bacteria, some kinds of which, otherwise indistin- 

 guishable, are distinguishable by their different reactions on 

 their media — we are obliged to conclude that there must bo 

 constitutional differences between the protoplasms they con- 

 sist of, and this implies structural differences. It seems that 

 structure and function must have advanced pari passu: 

 some difference of function, primarily determined by some 

 difference of relation to the environment, initiating a slight 

 difference of structure, and this again leading to a more pro- 

 nounced difference of function ; and so on through continuous 

 actions and reactions. 



§ 56. Function falls into divisions of several kinds ac- 

 cording to our point of view. Let us take these divisions in 

 the order of their simplicity. 



Under Function in its Widest sense, are included both the 

 statical and the dynamical distributions of force which an 

 organism opposes to the forces brought to bear on it. In a 

 tree the woody core of trunk and branches, and in an animal 

 the skeleton, internal or external, may be regarded as pas- 

 sively resisting the gravity and momentum which tend 

 habitually or occasionally to derange the requisite relations 

 between the organism and its environment; and since they 

 resist these forces simply by their cohesion, their functions 

 may be classed as statical. Conversely, the leaves and sap- 

 vessels in a tree, and those organs which in an animal 

 similarly carry on nutrition and circulation, as well as those 

 which generate and direct muscular motion, must be con- 

 sidered as dynamical in their actions. From another 

 point of view Function is divisible into the accumulation of 

 energy (latent in food) ; the expenditure of energy (latent in 

 the tissues and certain matters absorbed by them) ; and the 

 transfer of energy (latent in the prepared nutriment or blood) 

 from the parts which accumulate to the parts which expend. 



