320 PHYSIOLOGICAL REGULATIONS 



oxidation much faster than in heat turnover, and heat is lost mark- 

 edly slower (Chevillard, '35, p. 1046). It is said that heat may be 

 lost faster in the dead mouse than in the living one (Pincus et al., 

 '33). Control of the mouse over its temperature develops during 

 the first ten postnatal days (Pembrey, 1895; Sumner, '13; Ging- 

 linger and Kayser, '29). In the 2-day-old mouse compensatory 

 heat productions and their accompanying muscular movements 

 CPincus et al., '33; Stier, '33), are maximal in environments of 

 22° C; in still cooler ones the recovery becomes slower and less 

 successful, just as in the rabbit (fig. 149). Guinea pigs and some 

 other species, in contrast, are at birth fully armed with compensa- 

 tions for heat increments. 



Coefficients may be computed and compared in order to charac- 

 terize the convection systems, heating systems, and refrigerating 

 systems of animals. They are convenient parameters of conduc- 

 tion, permeability, emissivity, vaporization, radiation, and other 

 quantities. Some of these coefficients are constant under limited 

 conditions. But the so-called physical and chemical processes in- 

 volved are by no means fully identified ; so far as I can ascertain, 

 there is no relation between the constancy of a parameter of heat 

 exchange and the fact that an imputed process in it has a name. 



All the methods of comparing water exchanges appear to apply 

 also to the study of heat exchanges. Among species of diverse 

 body sizes and shapes, rates of heat production in turnover may 

 be set forth (Lambert and Teissier, '27; Benedict, '38, p. 131), and 

 related to supposed body surface area and to many other quanti- 

 ties. Velocity quotients, modification ratios, economy quotients, 

 tolerated loads, tolerance curves (fig. 152) and equilibration dia- 

 grams (fig. 150), are all applicable for comparisons. These quo- 

 tients, ratios and diagrams would be required for thorough charac- 

 terizations of modifications in thermal adjustments of animals such 

 as are produced in diverse lesions of nervous tissues (Brooks, '35; 

 Clark et al., '39) and many other states. Moreover these quanti- 

 ties in heat exchanges are directly comparable with the correspond- 

 ing quantities in water exchanges and other exchanges (see table 

 40), for most have the same dimensions. 



Differentiations may be made between increments of heat and 

 changes of heat balance. For, balance having been defined as a 

 point where gains equal losses, all the criteria of water balance 

 apply to heat balance. Heat load (AH) without change of heat 



