GENERAL FEATUEES OF WATER EXCHANGES 



179 



organs, the kidneys, an excess even more rapidly than does the 

 30-grani frog. 



Accelerations and decelerations of exchanges of water may be 

 compared quantitatively (table 14), in % of Bo/hour^. As men- 

 tioned, acceleration is apparently instantaneous in some species, 

 hence almost infinite. Deceleration appears to be slower than 

 acceleration in all living units studied ; it is greatest in unicellular 

 units. 



Hours 



Fig. 101. Courses of total water loads (% of Bo) during recoveries. Comparison 

 of water tolerance curves in 6 species, 3 to 21 tests being averaged for each curve. 

 At each time, the water load is taken as the mean difference of weight increments be- 

 tween the loaded individuals and the control individuals that were similarly denied 

 food but allowed water ad libitum. Dog, from figures 1 (A) and 10; rat, from figure 

 76; garter snake, mean from figure 81; frog, from figure 65; earthworm, from figure 

 88 and further data; Phascolosoma, from figure 85. 



For comparisons of tolerance curves, initial loads may be 

 equated. Then the relative loads in relation to time (figs. 102 and 

 103) epitomize those comparisons of eliminations already men- 

 tioned. From excesses of water, rats recover most rapidly of any 

 vertebrates. Invertebrates without special circulatory and excre- 



