350 PHYSIOLOGICAL REGULATIONS 



''bound," ''non-solvent," and the like, depending upon the many 

 procedures of measurement. However, for inherently related com- 

 ponents an increment of one is inevitably an increment of another. 

 Oxygen content may include the oxygen of oxyhemoglobin, may or 

 may not be represented by change of valence, may or may not 

 comprise the securities for its deficit. Each component is a bank 

 holding, and often it is, I imagine, the part of physiological secur- 

 ity to have little of it in cash. 



I find that the components for which I have presented quantita- 

 tive data are the very ones that have in the past been most fre- 

 quently mentioned as objectives of regulation. Bernard (1878) 

 specifically named water, heat, oxygen, hemoglobin, and acid. Hen- 

 derson ('17) added nitrogen, carbon, glucose, and others. The 

 number of components is almost infinite, since those not ordinarily 

 present in the organism (drugs, electromotive forces, parasites) are 

 also unloaded after they have gained access to it. Whereas the fact 

 of constancy in the content of each component has been stated, and 

 the organs by which mammals modify exchanges of it have been 

 examined, the possibility that the quantitative relations might be 

 similar among water, heat, and carbon dioxide has not been pre- 

 viously explored. It turns out that a remarkable parallelism 

 exists among the patterns of compensation of all. That fact allows 

 comparisons of the processes concerned in adjustments of each 

 component in common terms. But first, some properties that are 

 ordinarily identified with parts of the body instead of with the 

 organism as a whole will be mentioned. 



§ 124. Heart frequency 



Arbitrarily and tentatively, many physiological functions (com- 

 ponents) and their increments are assigned to particular organs or 

 tissues. Frequency of heart beat is named in connection with the 

 visible location of movement in the heart, though very many other 

 parts of the body are concerned in making possible, controlling, and 

 maintaining this activity (component). The situation is similar 

 to that for water, which is distributed through all tissues, though 

 when its volume or concentration in the plasma is measured, its 

 regulation is said to concern the plasma alone. Among com- 

 ponents to be considered in relation to topographical units of the 

 body, some concern known organs, others particular tissues, and 

 still others single cells and their parts. Parts and their functions 



