INTRODUCTION ( 



By the three aspects: modifications in exchanges, behavior to- 

 ward environments, and variability of contents, regulations are 

 to be described. Information that falls in these categories will be 

 the materials examined. 



§ 3. Extensions of the study 



Each of the three ways of studying self -maintenances of con- 

 stancies is applicable, so far as I can now ascertain, to all organ- 

 isms and portions of them (chapters XIV to XVI). All three can 

 be further studied (to limited extents) by interfering with what the 

 organism is doing, i.e., by surgical, pathological, or pharmacologi- 

 cal means, especially in breaking connections among its functional 

 units. 



One means of gaining insight into regulations is to observe to 

 what extents various animals are provided with them. Provisions 

 for correcting the contents of some components are absent or in- 

 complete to diverse degrees in immature animals. Or, comparisons 

 of species show regulations of a few components (as, heat) in some 

 but not in others. In some, regulations are faster than in others ; 

 in some they are lacking over certain ranges of bodily content. 

 Instances are found in which compensations become more rapid 

 with practice, and even in which non-existent ones may be called 

 into being. All these special instances may help in grasping how 

 self -maintenance is carried on. 



Any compensation appears as a correlation between content of 

 J and some feature of exchange. Of all the possible exchanges, 

 organisms are patterned to modify the exchange of J itself, which 

 alone restores the content of this particular component. To limited 

 extents, however, other contents and exchanges are modified (chap- 

 ters X to XII), usually to smaller extents. A study of the numer- 

 ous correlations among measurable properties yields a notion of 

 the number of strains suffered by the organism whenever it has 

 departed from balance of J. 



Further, each of the properties that is disturbed is itself under- 

 going adjustment toward restoration. That gives a picture of the 

 interrelations existing among components whereby simultaneous 

 processes act to bring the organism to its most persistent state 

 (chapter XVII). Only with violence to the organism does the 

 investigator study its components one at a time. Nevertheless, 

 after examination of what organisms do when single components 



