2 GROWTH: DEVELOPMENT: DECAY. 



decompose the simple compounds carbonic acid, water, 

 and ammonia by which it is surrounded, and use them 

 as material wherewith so to build up its own intimate 

 structure as to increase in size and weight, until that 

 boundary is reached which, on living things, is always 

 imposed. But this is not all that is implied in the term 

 growth ; for together with the building up there is always 

 more or less falling down, and the two processes of decay 

 and repair go on together ; the addition, however, is greater 

 than the loss, and so there is growth. 



With growth, too, there is development. Together with 

 the mere increase in size, to which alone the term growth 

 should be applied, there is a gradual change effected in 

 the structures of which a living being is composed, so that 

 they become more and more highly organized, and better 

 adapted to subserve those purposes for which they are 

 formed. 



Thus, by growth and development, a being attains such 

 perfection as is allotted to it, and in this state it remains 

 for a time. Then, having provided for the continuance of 

 its race, by setting aside portions of itself, with power to 

 grow up in the likeness of their parent, it begins to die. 

 Perfection gives place to imperfection ; instead of growth 

 there is shrinking ; instead of development there is dege- 

 neration ; and finally death ensues that state in which a 

 once-living structure decays, without renewal, and the 

 elements of which it is composed return to the inorganic 

 world, whence they were derived. 



Such is life as we see it in its simplest expressions, 

 and stripped of accessories, and such we find it in the 

 highest animal and in the lowest vegetable. The description 

 may seem to require some alteration here and there in its 

 application to individual examples; but the change re- 

 quired is more apparent than real, and the laws of birth, 

 growth, development, decay, and death, are such as all 

 living beings must obey. 



