412 PHYSIOLOGICAL REGULATIONS 



equation that relates two quantities under a variety of circum- 

 stances, is not needed before the interrelations may be analyzed 

 and represented as aspects of the organism's functioning. Count- 

 less are the circumstances in which heart frequencies have been 

 measured in man. All of these circumstances are associated with 

 change in some other measurable component, and often with known 

 loads of many components. Each load is a '^factor" in heart fre- 

 quency; whether each is a separate factor is a matter for definition 

 and for further study of relations. Hidden in the data of physi- 

 ology are, I believe, hundreds of clear correlations that have not 

 even been surmised, which nevertheless indicate how components 

 are related in the animal body. 



The physiologist may take advantage of the generalization that 

 every bodily function (component) is related to nearly every other. 

 Keys et al. ('38) wished to select persons who would acclimatize 

 advantageously to high altitudes. They, therefore, made eight 

 random measurements upon each of ten men ; later took those men 

 to the mountains for some weeks, and found which were able to do 

 most physical and mental work there. Correlations between the 

 initial measurements and the later performances revealed what 

 combinations of physiological characteristics were best suited to 

 life in the mountains. The important feature is that any set of tests 

 may serve as a basis for discovering a given physiological aptitude. 

 No one need know what constituent processes are at stake in the 

 particular acclimatization; ''blind" trials upon random individuals 

 will furnish the information needed for extensive predictions. 



In the end, physiology has a set of relations similar to what 

 anatomy has in "Cuvier's Law." Cuvier (1827, p. 83) realized 

 that he could pick out bones belonging to one species of animal from 

 a mixture, and predict the conformation of the jaw and teeth from 

 that of the claws. ' ' Every organized being forms a peculiar sys- 

 tem of its own, all the parts of which mutually correspond." Simi- 

 lar statement is frequently possible in physiology and in functional 

 pathology, as has long been shown in medical practice. Just as a 

 hypertrophied heart often accompanies unusually high arterial 

 blood pressure, so deficit of salt often accompanies modified func- 

 tion of adrenal glands. To say that one can see no ''connection" 

 between what these small glands are metabolizing and what the 

 whole body is metabolizing may be correct; but that statement 

 blurs an interrelation, which holds even though in some bodily 



