456 PHYSIOLOGICAL REGULATIONS 



minima, and all the rest. Each is a rate of loss or of gain measured 

 at the load that most favors conservation. 



Is there ever ''minimal work" in the sense of the well-known 

 theorem of mechanics? There it is postulated that the sum of the 

 energies expended tends to be the least that can accomplish the 

 work performed. Perhaps the question cannot be answered in 

 organisms so long as chemical and other processes appear insepar- 

 able from mechanical ones. No rigorous solution is likely at 

 present and in a long future, for plainly, identification of minimal 

 work requires a knowledge of all transformations that are going 

 on. In the organism this probably means recognizing all the cor- 

 relatives of a given exchange. It was noted, for instance, that 

 water exchange is concerned not only in water equilibration but in 

 heat, solute, and synthetic exchanges. Many of its relations are 

 unknown even qualitatively and others may hardly be measured 

 quantitatively ; and so it is for such other components as have been 

 widely studied. To circumscribe the system would defeat the re- 

 search. Were enough factors considered to bring the result that 

 the work performed was approximately minimal, the outcome 

 would be believed ; if the result were not approximately minimal, 

 the investigator would cast around for other modifying factors. 

 That is mere toying with the rules of thermodynamics. There is 

 always the guess that death would be cheaper than maintenance. 



(2) Capacities. Equilibrations reveal highest rates of ex- 

 change far above the minimal; the uniformity found is that high 

 and low rates of total gain appear ' ' spontaneously, ' ' each in loads 

 of opposite sign. The maximal rates roughly indicate the extent 

 of provisions for recoveries. Doubtless these ''capacities" for 

 increase in exchanges could be classified as showing anatomical fac- 

 tors, chemical factors, muscular factors, and the like. One of the 

 favorite methods of physiology is to embarrass the living unit by 

 interfering with what goes on. Indeed, experimentation is largely 

 an inquiry into the vulnerabilities whereby loads can be imposed 

 and recoveries be modified. Thus, rates are compared after re- 

 moval of pancreas, privation of food, cutting of nerves, introduc- 

 tion of agents, or believed inhibition of enzymes. Occasionally an 

 "interference" is found that enhances the rates of particular ex- 

 changes ; often it is inferred too that this confers an ' ' advantage ' ' 

 that the organism did not have before. I imagine the organism is 



