CHAPTER YII. 



THE SCOPE OF BIOLOGY. 



§ 3Y. We are now in a position to map out the boundaries 

 and divisions of our subject. Grouping together the general 

 results arrived at in the first three chapters, and joining with 

 them the results which the last three chapters have brought us 

 to, we shall be prepared to comprehend the science of Biology 

 as a whole ; and to see how its truths may best be classified. 



In the chapters treating of Organic Matter, the Actions of 

 Forces on it, and its Reactions on Forces, the generalizations 

 reached were these : — that organic matter is specially sensi- 

 tive to surrounding agencies ; that in consequence of the 

 extreme instability of the compounds it contains, minute dis- 

 turbances can cause in it large amounts of re-distribution ; 

 and that during the fall of its unstably-arranged atoms into 

 stable arrangements, there are given out proportionately 

 large amounts of motion. "We saw that organic matter is so 

 constituted, that small incident actions are capable of initiat- 

 ing great reactions — setting up extensive structural modifica- 

 tions, and liberating large quantities of power. In 

 the chapters just concluded, the changes of which Life is 

 made up, were shown to be so adjusted as to balance outer 

 changes. And the general process of the adjustment we 

 found resolves itself into this ; that if in the environment 

 there are any related actions, A and B, by which the or- 



94 



