SOME SPECULATIONS CONCEBNING REGULATIONS 461 



face for output, hoping thereby to quantitate my elimination and 

 to adjust its rate to my water content. Later I would set aside 

 another area of surface for intake ; then I could afford to make the 

 remaining surface impervious to water if opportunity ever arose. 

 I would laugh at any one who thought he could find out why I had 

 done all that. But I would be interested in asking how it is done, 

 even though there were no chance of taking my machinery apart 

 without stopping it all. 



In some such vein the imagination can go on replacing the un- 

 swerving history of organisms by anthropomorphic argument. 



§ 168. Forces in biological equilibria 



Forces are ordinarily classified in terms of the procedures for 

 their physical measurement. Their identification in living proc- 

 esses is usually circumstantial, the potential as found being ascer- 

 tained to be sufficient to push, but never known to be that which 

 does push. 



The data presented in this work might be supposed to contribute 

 more to physiology if the rates of exchange were translated into 

 equivalent forces. By habit and assumption, to decide that an 

 event in an organism can be analogous to a process that has a dy- 

 namical magnitude and name, appears to many biologists to be 

 something accomplished, however indirect the inference. I take 

 the view that the rates, actually measured, lead to fewer illusions 

 than do those circumstantial equivalents. It is easy to obscure the 

 relations among facts by translating them into imagery so alluring 

 that fiction is taken for reality. When the poetry is later rejected, 

 with or without the expenditure of much labor to separate out the 

 materials upon which it was built, the materials also are often lost 

 or discredited. 



Forces are suggested when the component being equilibrated is 

 water; and it would be a usual guess that osmotic pressures are 

 concerned in exchanges. For Arbacia eggs most persons would 

 agree ; for frogs some would agree in part ; for whole dogs probably 

 no one would agree. The quantitative estimation of those forces 

 would be subject to still less agreement. Intake of water by mouth 

 in dogs happens to be known to involve nerves and muscles that can 

 no longer be described as exhibiting only forces of osmotic pressure, 

 while in frogs intake is scarcely known to involve more than the 

 skin, which corresponds in some respects to the pictured membrane 



