470 PHYSIOLOGICAL, EEGULATIONS 



alone is named as correlative, and if investigation stops with it, a 

 special role may be imputed to it. Or, supposition is reinforced 

 with colorful language, such as that a living unit is like a dynamo, 

 or a paint mill, or a gelatin block. Or, spice of associations sug- 

 gests that all living things are dilute water. Most of those state- 

 ments can be tested, and definitions, criteria, and experiments 

 designed accordingly. But the charm of the speculation is occa- 

 sionally lost when tests are undertaken. 



Finally there are speculations which seem predestined to be 

 fruitless. Origins, purposes, and entelechies will probably never 

 be demonstrated in the way that rates of exchange and their corre- 

 lations have been. But that is a speculation, too. 



