364 PHYSIOLOGICAL KEGULATIONS 



quotients) near balance, the smaller the variability. Data are at 

 present not sufficient to decide how widespread this relationship 

 may be. 



What is the normal state of an organism, a term that everyone 

 uses but no one defines? Every biologist has a concept of the 

 norm; precise meanings can only be quantitative ones, I believe. 

 Heretofore I have spoken of normal individuals or states as being 

 the controls that are compared with others in which some load pre- 

 vails. They are considered to have zero load of whatever com- 

 ponent is being measured. On the basis of variations I am able to 

 affirm further what latitude may be expected in their content of 

 any one or several components. A single measurement may be far 

 from the mean, but among a number of measurements the content 

 is represented by the standard deviation of the observations. The 

 deviation thus helps to define the normal state and aids in charac- 

 terizing the organism in the same manner that listing the condi- 

 tions of environment or of observation does. 



But whereas variability could be measured under numerous 

 conditions, the normal state is also that in which measurable kinetic 

 equilibrium of a specified component prevails, that is, where gain 

 of it equals loss. It is a particular stationary state of common 

 occurrence. However, the turnovers also vary more or less, for it 

 is rarely possible to demonstrate that gain exactly equals loss; 

 errors of measurement, the ''hunting" of supposed governors, and 

 the durations of the period in which the exchanges are measured, 

 all being factors. Hence the normal state varies by a precision 

 (§23) as well as by a content. 



As usual, then, it is found that the normal state or norm has no 

 meaning except as it is defined. It can never be given an absolute 

 or complete definition, but approximations are obtained by listing 

 conditions, states, contents, exchanges, numbers and kinds of indi- 

 viduals, and variabilities of each. The norm for any component 

 reflects preponderantly those very events in organisms that con- 

 stitute maintenance of physiological state. 



"^ 132. Behavior and maintenance 



The study of animal behavior, which is sometimes regarded as 

 mere tabulation of what responses are elicited by each kind of 

 stimulus, also contributes to understanding maintenances. A man 

 at rest finds himself cold. He, perhaps subconsciously, moves to 



