312 PHYSIOLOGICAL EEGULATIONS 



more than rates of heat production. Rates of production do not 

 much vary with those loads that prevailed, in the particular indi- 

 viduals studied at physical ''rest." (3) Recoveries from deficits 

 are slower than recoveries from equal excesses. Speculating, I 

 imagine that recoveries from deficits might "cost" more if stored 

 potential energy were expended in faster heat production. (4) 

 Rates of loss by three separable paths of heat loss (vaporization, 

 convection plus conduction, radiation) are all increased in positive 

 head loads. (5) But quantitatively, vaporization plays the great- 

 est role in modifying the rates of heat exchange. (6) Roughly the 

 partitions among paths indicate the order in which various cooling 

 devices are turned on and off. 



Each of these conclusions is analogous to one drawn for water 

 exchanges and equilibration in man, heat replacing water in the 

 relations examined. In a word, heat content is recovered in the 

 presence of any heat load, by modifications in appropriate direc- 

 tions of those exchanges that are already operating. No one path 

 of exchange is alone concerned, but "physical" compensations 

 (losses) are more greatly modified than "chemical" ones (gains). 



§ 115. Heat exchanges of babbit 



(1) Maintenance of heat content in the rabbit is such that, ac- 

 cording to Gasnier and Mayer ( '34) the rectal temperature does 

 not ordinarily change as much as 0.1° C. within one hour. Ex- 

 changes of heat during turnover may be analyzed according to 

 paths. In periods of 0.25 hour in a calorimeter, rates of three heat 

 losses (fig. 148) varied by amounts roughly proportional to their 

 mean magnitudes. 



Is it possible that gain of heat is steady while loss of heat fluc- 

 tuates, the two being equal only on the average"? That is a ques- 

 tion asked by Gasnier and Mayer ('34). They did not measure 

 total heat gain in short successive periods, and no suitable data on 

 variability of rate of gain seem to exist for the rabbit. Assuming 

 that heat production is constant within the deviation of its measure- 

 ments, they drew the tentative induction that loss hunts about (in 

 the sense of a mechanical governor) to keep pace with gain. The 

 theory is that a rate that varies little (gain) is setting the pace 

 for a rate that varies much (loss) ; one is inflexible while the other 

 takes care of discrepancies between them. The little flywheel 

 (loss) does more clumsily but fitly what the big flywheel (gain) 



