376 PHYSIOLOGICAL EEGULATIONS 



in exercise (man), lactic acid and oxygen in exercise (man), and 

 excitability and lactic acid in stimulation of nerve (frog) constitute 

 pairs that move at very different rates, but in nearly the same ratio 

 in both directions. Either reversed processes or matched "gover- 

 nors" may be at work in the two states (II and IV) of the organ- 

 ism. Actually the processes usually do not occur in the same 

 paths, for example the gain and the loss of water. A difficulty in 

 phrasing a more general induction is that the maximum attained 

 by the load often is itself bound up with compensation and recov- 

 ery, the asymptote of loading (state III) being already an expres- 

 sion of rapidity of recovery. 



Intermittency of rate occurs in a great many components (limb 

 movement, sleep, reproduction), and for the most part it is ignored 

 in their study. The dog accomplishes by intermittent ingestion of 

 water exactly what the frog accomplishes by nearly continuous 

 imbibition of water. Intermittency is a convenience to the organ- 

 ism in permitting it to go about other activities which preclude the 

 exchanges in question. The dog devotes perhaps 0.5 per cent of 

 its life to drinking, 2 per cent to eating, 1 per cent to micturition, 

 30 per cent to sleeping, and so forth. Segregation of each allows 

 greater variety of undertaking in all the remainder of the time. 



Rates of recovery in organisms are modified by many agents 

 and conditions. Loss of water, gain of heat, and loss of lactate, 

 are all accelerated by moderate physical exercise in man. Glucose 

 removal by dog is changed by previous glucose administration, by 

 deprivation of adrenal glands, of pancreas, and of liver. Carbon 

 monoxide is removed faster when oxygen, or oxygen + carbon 

 dioxide, is breathed. Results of experiments, treatments, and 

 therapies may be suitably measured, of course, as modifications of 

 loads (tolerance curves) and of rates (exchange curves). It 

 appears to be exceptional, as was said, to find agents that modify 

 one component only. 



Rates of exchange show acclimatizations. These are progres- 

 sive changes in rates incident at given loads, that appear after con- 

 tinued or repeated loadings. Time is required to bring them forth. 

 Thus, repeated administrations of water to a dog result in greater 

 rates of urinary output at the same water excess (Kingsley). The 

 rate of heat loss increases upon successive days of exposures to hot 

 atmospheres (Adolph and Dill, '38). Less chloride is lost through 

 the skin in sweat upon successive exposures to hot atmospheres 



