446 PHYSIOLOGICAL EEGULATIOlSrS 



tissue temperature in each part of a man. That might justify des- 

 ignation of an equilibrium as a complacency (Raup, '26). Appar- 

 ently the particular content at which the human organism is in 

 balance recurs just as inevitably as it does in any other sort of 

 system at equilibrium. Other organisms, as the turtle, are indif- 

 ferent toward a wide range of temperatures. Turtles modify their 

 coefficients of heat exchange only at high positive loads, and not at 

 others; in addition they exhibit behaviors of shunning extreme 

 temperatures that are effective in preventing extreme loads. 



Maintenance is probably less commonly a cessation of activities 

 of the organism (static) than of recovering their usual rates after 

 displacement (kinetic). Measurements of rate therefore describe 

 the equilibrium of the organism ; what it tends toward rather than 

 what it keeps. The contrasts between rates during displacement 

 or load and the rates at equilibrium are the very features that 

 emphasize regulation. The terms "homeostasis" (Cannon, '32), 

 "complacency" (Raup), and others, possibly imply a static system. 

 Any other new term such as "homeokinesis" will in its turn become 

 inadequate as concreteness is gained; hence my determination to 

 get along with older terms such as equilibration (Spencer) and 

 regulation (Bernard). Moreover, the quantitative aspect of regu- 

 lation will hardly be adequately represented by any word. 



§ 161. Multiple eegulations 



It seems as though the number of components regulated and the 

 types of their loading is almost limitless. For, not only can new 

 components be investigated, but components can be subdivided and 

 grouped; and the rates of rates (accelerations), and even changes 

 in acceleration, can be added. The conditions as well as the phy- 

 siological states may differ in a semi-infinite variety of combina- 

 tions to yield new types of increment for each measured component. 

 Certainly the distinctions among types and varieties cannot be 

 ignored, and one way of limiting the study in practice is to agree 

 on arbitrarily standard conditions and species. Another is to 

 study many recoveries simultaneously in a single individual, lead- 

 ing to an understanding of multiple regulations. 



Regulation of some particular component is isolated only as a 

 scientific tour de force, the isolation and definition usually depend- 

 ing on methods of measurement and on conditions imposed upon 

 the organism. For the complete description of a regulation, the 



