4 PHYSIOLOGICAL REGULATIONS 



The peculiar method of this description is to use detailed and 

 quantitative materials to lead up to a picture of certain types of 

 regulation. Then the maintenance of a specific constancy in an 

 organism may appear no longer as a conjecture or a pronounce- 

 ment, but as a conclusion from many observations. Regulation 

 takes on a patterned, and at times a geometrical, concreteness. 

 Heretofore the abstraction of regulation has been an accepted part 

 of physiology, though often regarded more as a frill than as an 

 inevitable aspect of everyday phenomena. Usually it is conceived 

 in the form in which Claude Bernard (1878, p. 144) presented it. 

 He postulated that "in animals having free existence there neces- 

 sarily exists a group of arrangements controlling the losses and 

 the gains in a manner that maintains the quantity of necessary 

 water in the internal medium" of the body. A quantitative de- 

 scription of any considerable group of such arrangements has been 

 given only for blood (Henderson, '28) ; and blood has commonly 

 been referred to as though it were a special sort of system, as 

 though to it alone did that scheme for representing interrelations 

 apply. 



By sifting and putting together selected data I ascertain what 

 occurs when some quantity (content) of the organism gets too large 

 or too small for continuance. In this way a circumscribed func- 

 tioning of the organism is quantitatively described, which later 

 (chapter XIX) proves to be a part of a larger functioning. 



§ 2. How REGULATIONS MAY BE STUDIED 



The approximate definitions of regulations, indicated above, at 

 once suggest means of investigating them. What procedures are 

 available for measuring constancies in living bodies, and what 

 features are present by virtue of which the constancies are per- 

 petuated? I think that there are broad categories of measure- 

 ments which characterize the maintenances of all sorts of proper- 

 ties, and that in the end it will be quite unnecessary to restrict 

 specifications to water content or to heat content or to any other 

 one. The following phenomena appear to be implicated. 



(1) Exchanges. In a stationary state which is the organism, 

 constancy of content means a rate of gain equal to a rate of loss. 

 But, of numerous components, as water, animals do not character- 

 istically have equal inflow and outflow in every minute of life. 

 Both undergo endless fluctuations. They are compatible with con- 



