IN LIVING MATTER 19 



the same factors, namely, the values of the potential factors and 

 the facilities for interaction. 



Hence the state of equilibrium Qr reaction may be disturbed 

 by addition or removal of energy so as to disturb the potential 

 factors, or by alterations which change the ease of passage from 

 one form to another. 



It is the variation in the potential factor or intensity factor 

 which appeals to our sense organs, and determines the results of 

 all physiological stimulation, and it is for this reason that the 

 potential factor and methods for measuring variations in it l were 

 known to mankind long before the recognition of corresponding 

 quantities of energy. 



CHEMICAL ENERGY AND CHEMICAL EQUILIBRIUM 2 



The energy changes which interest us most in connection with 

 the biological chemistry of the cell are those in which chemical 

 energy plays a part, and accordingly we pass on to the energy 

 conditions in a solution. In order to simplify the matter we shall 

 assume at first that there is no catalyst present, and investigate 

 the equations governing energy changes in solution under different 

 conditions in which energy interchanges are possible between the 

 various forms of energy which can react in the solution. That 

 is, we shall leave out of consideration at present the mechanisms 

 by which the energy changes are brought about, which can alter 

 the velocities with which the changes occur, or which, by bringing 

 into play other forms of energy, can alter the conditions of reaction 

 and the equilibrium point. 



The three forms of energy which normally undergo alteration 

 in value when a chemical reaction occurs in solution 3 are the 

 chemical energy, the heat energy, and the osmotic energy. The 

 law of conservation of energy teaches that the algebraic sum of 

 the three alterations must be zero. Or, if C represent chemical 



1 Such, for example, as the thermometer in connection with heat energy, the 

 monometer in connection with volume energy. 



2 The student who is unfamiliar with the mathematical method followed in 

 the subsequent pages can omit the proof given therein, and confine himself to 

 the experimental and more practical part of this subject. (Editor's Note.) 



3 Or, in gaseous form, the investigation is the same for both conditions of 

 matter. 



