THE ENERGETICS OF ORGANISMS 99 



organism with the strictness to which they apply to the inanimate 

 system. 



38^. Qualifications of the above Statement. Living 

 phenomena that can be observed are (for instances) : motions, 

 quantities and natures of materials taking part in a reaction, 

 velocity of a nervous impulse, frequency of nervous impulses, 

 rate of flow of the blood, viscosity of muscle-substance, tension 

 of a muscle, electric potentials developed by a muscle contrac- 

 tion, or a nervous impulse, oxygen inspired, CO 2 expired, reaction 

 time, and so on. 



There are also pleasure, pain, feeling, consciousness in general 

 and so on. These are obvious life-phenomena for the experi- 

 menter and, irresistibly by analogy, for other men and women 

 and animals. 



Precise physiological results take the forms of equations such 

 as that quoted above for the energy-balance. Such equations 

 are (relatively to physical science) few in physiological investiga- 

 tions. In general an equation, such as we are now considering, 

 takes the form 



F = f(m, n, 0) 



F is some function of the variables, m, w, 0, so that when 

 m, «, are given definite values, the form of the mathematical 

 function enables us to find F in a perfectly definite way. (There 

 are, of course, experimental errors which the physiologist can 

 positively appraise.) 



F must be of the same denominations, in a physical sense, as 

 m, w, o. Fy for instance, may be some quantity of heat energy 

 expressed in calories, and so reducible to absolute units of 

 energy ; m, n, o may be quantities of heat, or electric potential, 

 of mechanical work, of water synthesized, etc., and so also 

 reducible to absolute units. Both sides of the equation must 

 involve physical quantities which are fundamentally the same. 



Now feelings^ consciousness ^ etc.y cannot be equated to mass, heat, 

 electric potential, etc. (and thus the well-known relation which 

 connects increments of sensation with increments of stimulus is 

 not an equation recognizable by mathematical physics). 



Therefore obvious living phenomena may not always be put 

 into mathematical-physical relations with obvious life-phenomena 

 which can be given precise physical values. 



