y 



472 PHYSIOLOGICAL EEGTJLATIONS 



atmosplaeres when in water deficit ; that preference tended to main- 

 tain the water content, too. The amount of water in the body 

 fluctuated to a degree characteristic of each species. For the 

 understanding of all those regulations, only measurements of water 

 content, water exchanges, and time were required. 



A diverse type of water increment resulted from each experi- 

 mental procedure that induced the increment. There were dehy- 

 drations by privation of water, by injection of sucrose, by drainage 

 of pancreatic juice, by exosmosis. Some of the types kept the ani- 

 mal in a stationary state of water increment. Diverse shifts of 

 water balance itself also were noted, indicating that from day to 

 day the total water content might be maintained at progressively 

 different amounts. 



Not only whole organisms from man to ameba, but as well 

 diverse parts of organisms from blood volume to single cell, mani- 

 fested similar regulations. Each equilibrated its usual content 

 according to a common pattern, but by a variety of paths of ex- 

 change. Comparisons of rates of exchange, modifications in those 

 rates with water increments, variabilities of content, and prefer- 

 ences for diverse aqueous environments, distinguished quantita- 

 tively each sort of living unit. 



Further understanding of water regulations was sought in vari- 

 ables other than water increment, water exchange, and time. 

 Simultaneous compositions of parts (tissues), volumes of parts, 

 body sizes, and metabolisms of many kinds, were accordingly corre- 

 lated with those variables. Inklings were thereby obtained con- 

 cerning the intermediary processes of water exchange, and the 

 numerous relations of water that are strained by the one stress of 

 water increment. Each increment of water could in fact be charac- 

 terized by the contents and exchanges of a whole set of its correla- 

 tive components. Various methods were worked out of represent- 

 ing these numerous correlations ; each species and part was thereby 

 differentiated numerically within a pattern that was common to all. 



Altogether, a detailed description of water relations of living 

 units resulted. Only those relations that seemed implicated in 

 processes of regulation were included, but they were many (chapter 

 XIII). Water content appeared to be fixed by virtue of all the 

 other constant properties of the organism ; the many fixed the point 

 to which the one would return after each disturbance. 



Using analogous measurements and correlations, I could now 



