310 



PHYSIOLOGICAL EEGULATIONS 



calorimetry, being in common, tends to confuse two separate 

 measurements ; it is clear that only in heat balance, and on the 

 average, does one equal the other. It may also be emphasized that 

 gain is more than that by oxygen utilization when radiations or 

 diathermy are received by the body. 



Change in rate of heat production is sometimes termed ' ' chemi- 

 cal" regulation of body heat, while change in rate of heat loss is 

 called "physical" regulation. Often both designations are lim- 

 ited to changes occurring under particular circumstances. The 

 terms actually identify the two directions of the physiological heat 

 exchange with two recognized varieties of energy transfer. 



o 



4- 



t - 





 -2 



+4 



+2 



Hea+ Load ~Cci\.jVc^. 



Fig. 147. Eate of total heat loss, and its partition, in relation to heat load during 

 recovery. Vaporization is latent loss; convection plus radiation is sensible loss. The 

 positive load was previously created by physical exercise indoors. The same single ex- 

 periment of Hardy et al. ('38), as in figure 146. The negative load resulted from 

 drinking cold water one hour previously; Pinson and Adolph ('42). 



"Physical" compensation of heat content occurs in the diminution 

 of loss rate in heat deficits as well as in increase of loss rate in heat 

 excesses. But "chemical" compensation of heat content in man 

 appears to be insignificant or sometimes non-existent in either 

 direction, as in the particular data cited here. These facts become 

 emphatic upon contrasting heat regulation with other regulations. 

 Within one hour all recoveries from heat excesses are 70 per 

 cent complete. The values of net velocity quotients for heat 

 (1/At) fall between 0.7 and 1.2/hour. Recoveries from deficits are 

 the slower, even in the interval of time when maximal quotients 

 are found. Often the body rewarms without extra production of 

 heat; heat is simply lost more slowly. Probably certain environ- 

 mental conditions could be found in which the relative rates of 

 recoveries would be inverse to those here represented. 



