HEAT 321 



balance (Ho) does not stay constant in any circumstances that al- 

 low of recovery. In practice, endless arguments arise as to 

 whether in a state of hyperthermia (fever) or hypothermia (1) the 

 "thermostat" of the organism has changed its setting or {2) there 

 is an aberrant imbalance between gain and loss of heat. Once 

 criteria such as those suggested have been adopted, the question 

 can be answered by calorimetry in every instance. By speculation, 

 one chooses between (la) assuming the existence of a second regu- 

 lator to ''reset the thermostat," which presumably means there are 

 two or more superimposed thermostats, and (lb) regarding a shift 

 of heat balance as a concatenated member of a large group of 

 interacting quantities. 



Enough has been set forth to indicate that investigation of heat 

 regulation yields the same sorts of quantitative relations as does 

 water regulation. In particular, the tolerance curve and the 

 equilibration diagram relate the rates at which restoration occurs 

 to each increment of heat load. Evidently this sort of physiologi- 

 cal pattern is not limited to biochemical entities such as water that 

 have particular kinds of absorptive and emunctory organs at their 

 disposal. Heat is an entity of a different category, with entirely 

 different arrangements physically, anatomically, and physiologi- 

 cally concerned in its exchange. When similar patterns emerge 

 among supposedly dissimilar processes, it becomes profitable to 

 take the tentative view that diverse kinetic equilibria can be studied 

 independently of the specific forms of machinery present. 



§ 117. Summary 



Maintenance and recovery of mean body temperatures (heat 

 contents) may be described by means of relations of heat exchanges 

 to heat contents. Partial data exist for man, rabbit, mouse, and 

 some other species. Variability of heat content may be viewed as 

 a resultant of the variabilities of heat gai^is and heat losses. 

 There are slight indications that heat losses may be more con- 

 cerned in compensating for the unsuitabilities of heat gains than 

 vice versa. Further, losses by vaporization may through succes- 

 sive modifications compensate for ordinary fluctuations in sensible 

 losses, and vice versa. 



Equilibration of heat content may be characterized in the same 

 ways as the air-conditioning of a building that has an installed 

 thermostatic equipment. Variabilities in diverse conditions, and 



