26 Evolution and Adaptation 



to the destruction of the young, is manifestly disadvantageous 

 to the race. As soon, however, as we enter the field of so- 

 called abnormal developments, the adaptive relation of the 

 organism to its environment is very obscure ; and yet, as in 

 the case of adaptation to poisons, we see that we cannot draw 

 any sharp line between what we call normal and what we call 

 abnormal development. 



Comparison with Inorganic Phenomena 



The preceding examples and discussion give some idea of 

 what is meant by adaptation in living things. In what respects, 

 it may be asked, do these adaptations differ from inorganic 

 phenomena ? The first group of inorganic bodies that chal- 

 lenges comparison are machines. These are so constructed 

 that they may be said to accomplish a definite purpose, and 

 the question arises whether this purpose can be profitably 

 compared with the purposefulness of the structure and 

 response of organisms. That the two cannot be profitably 

 compared is seen at once, when we recall the fact that the 

 activity of the machine is of no use to it, in the sense of 

 preserving its integrity. The object of the machine is, in 

 fact, to perform some useful purpose for the organism that 

 built it, namely, for man. Furthermore, the activity of the 

 machine only serves to wear it out, and, therefore, its actions 

 do not assist in preserving its integrity as do some, at least, 

 of the activities of an animal. It is true, of course, that in a 

 mechanical sense every action of the organism leads also to a 

 breaking down of its structure in the same way that a machine 

 is also worn out by use ; but the organism possesses another 

 property that is absent in the machine, namely, the power of 

 repairing the loss that it sustains. 



One of the most characteristic features of the organism is 

 its power of self-adjustment, or of regulation, by which it 

 adapts itself to changes in the environment in such a way 



