390 PHYSIOLOGICAL EEGULATIONS 



excretion. Conversely, the multifarious contents and exchanges of 

 any one component are manifested in loads of many other com- 

 ponents. Hence it is possible to compare, for instance, the rate of 

 water excretion or ingestion in relation to diverse loads of each of 

 several components (§80). Various "reactions" of compensation 

 and defense are commonly recognized in pathological science 

 (Bloom, '40), each of them representing a load or a rate that accom- 

 panies some particular type of disturbance of usual content. 



Several parts of one organism are simultaneously recovering 

 from the load of the whole with respect, for instance, to water or to 

 glucose. Every cell, tissue, organ, and organism has its own recov- 

 ery rate; and comparisons among the simultaneously observed 

 units may be as extensive as the data. Whereas blood and liver 

 may be alike in rates of return of water load, they may be enor- 

 mously diverse with respect to glucose exchange. Their diversities 

 express in quantitative fashion those divisions of labor that have 

 been the objectives of much study. For, "special functions in spe- 

 cial tissues" has been a mainstay of physiological concepts since 

 Galen. 



§ 141. Species 



Data such as have been presented in previous chapters furnish 

 materials for physiological characterization of individuals, species, 

 and classes of animals. They also extend to cells and organs. 

 "What are some of the manners in which they may be arranged 

 to this end? 



It was found practical (<§ 70) to distinguish numerous species, 

 in respect to a single component, by their rates of turnover, their 

 rates of maximal exchange, etc. With data now at hand for sev- 

 eral components in one species, further differentiation is in order. 

 A list of components and exchanges such as is shown in table 40 

 characterizes, I judge, only one species. Certainly the list for 

 man differs significantly from that for dog (table 42). I believe 

 the relative quantities can suffice to show the difference, inde- 

 pendently of the absolute or physical units there employed. 



Equilibration diagrams serve as epitomes of most of what is 

 known concerning regulation of each component, and a book of 

 such diagrams might be composed for one species. Or, adopting 

 a uniform arrangement and set of scales for all the materials, 

 several components may be put in direct comparison in one dia- 



