250 PHYSIOLOGICAL, KEGULATIONS 



water in blood is equivalent to a large load of water in the whole 

 body. 



Among metabolic events, water content brings large changes in 

 clearances of several solutes through the kidneys (Kaplan and 

 Smith, '35). Rates of excretion of chloride, sodium, calcium, inor- 

 ganic phosphate, and nitrogen increased 4 to 11 fold during 4 hours 

 of continued water administration (Misawa, '27). Some of the 

 chloride came from heart, lung, and spleen according to the analy- 

 ses represented in table 26, column 5. In contrast, excretion of 

 magnesium did not change and output of potassium decreased. 

 The decrement of sodium and the retention of potassium in the 

 body are opposed to results reported for man (§88 (3)) at smaller 

 + AW. Whatever the relations of chemical comjDonents to water 

 in the rabbit, it is evidently impossible to suppose they all behave 

 alike in the presence of water excesses. Planned attempts to iden- 

 tify changes in the contents of each of these electrolytes in six 

 tissues of rabbits in positive water loads revealed no consistently 

 significant modifications in any (Wada, '33) ; more samples at 

 fewer times would perhaps have yielded significant results. 



The rabbit appears to be characterized in water loads by large 

 increments in dilution of blood and skin, and small modifications 

 of muscle, as compared with dog. Whatever this means in terms 

 of tissue functioning, it indicates that when the experimenter dis- 

 covers that a rabbit is more convenient than a dog in providing 

 suitable quantities of materials for analytical procedures, he does 

 not virtually analyze a dog, or vice versa. 



§91. Rat 



Tissue compositions in this species change during absorption of 

 a dose of water from the alimentary tract (Heller and Smirk, '32a, 

 p. 16). Dilutions, as measured from dry residues, indicate that the 

 partition of water between liver and leg muscle is uniform, but the 

 first tissue is diluted more than the whole body, the other tissue 

 receives less water than its proportional share (table 29, column 5). 



Young rats were subjected to prolonged restriction of water 

 intake by Jackson and Smith ('31b). Just enough water to main- 

 tain a body weight of 60 grams was allowed at all ages. When 

 autopsied, all the tissues tested contain somewhat less water rela- 

 tive to their dry content, than control rats of the same age (but 

 greater size), or than rats of the same size prevented from growing 



