Habit. 317 



be destroyed in the next. But we have found that as a matter of fact 

 the work of one age has served for a basis for the work of the succeed- 

 ing ages, and that by reason of the general persistence of the forces at 

 work, there has never been a cessation of life on earth since life first be- 

 gan. Such modifications as ma}' have taken place in any of these con- 

 ditions as the geological or geographical have been so slow as to en- 

 able the habits of organic life, as a whole, to become modified corres- 

 pondingly, while as to that other series of essential factors compre- 

 hended under the phrase, radiant energy of the sun, they have remained 

 practically constant and identical ever since life began on earth. 



It appears, then, that habit depends upon force applied from without. 

 In the case of lungs, for example, there are two bodies held apart, or 

 at least parted, by force ; viz. , oxygen and carbon, the first outside of a 

 skin, the second inside of it. Brought into each other's neighborhood, 

 the carbon so comminuted by the digestive process as to be subject to 

 the chemism of the oxygen, the latter penetrates the skin, separating 

 the two and forms its union, and then as carbonic acid it passes back 

 through the skin. This is the habit of respiration, and it specializes 

 the part of the skin thus acted upon, into lung tissue. It is thus that 

 habit differentiates, and that the function forms the organ, and the 

 habit is that of the environment first, and after the differentiation the 

 form of the part is such as to respond to the force that formed it, and to 

 that force alone, or more readily to it than to any other. This facility 

 of being acted upon by such energy or force indicates its differentiation, 

 and the frequency and uniformity with which the action of the energy 

 takes place constitutes its habit. The energies which act upon us and 

 drive us to do whatever we do, are so familiar to us, and we have be- 

 come so nicely adjusted to them through the habits of so many genera- 

 tions of ancestors, and respond to their influences with such facility, 

 that we do not realize that our actions are so little our own. From what 

 has already been said, we must begin to see that the forces of nature 

 build up and tear down organisms, and that everything vital as well as 

 everything inorganic constitute the mere playthings of these forces. 



From what has been said in former chapters in regard to adaptation, 

 it is obvious that it is not essentially progressive. The dynamic agen- 

 cies by which the earth is surrounded, permeated and influenced, keep 

 up a continual hubbub and movement amongst all its occupants. Races 

 of organisms, like individuals, have their periods of infancy, growth, 

 culmination, decline and extinction. After the culmination of a race 

 its struggle for life is a losing game. In order to adapt it to changing 

 conditions nature amends, reforms, adds to, subtracts from, patches and 

 alters until there is no place left for a patch that will do an}' good, then 

 she abandons it to its fate and turns her attention to a new one. Ex- 



