210 PHYSIOLOGICAL EEGULATIONS 



In dogs subjected to either positive or negative water loads the 

 reputed plasma volumes (Hb, VR, T1824; fig. 114) change by 

 larger fractions than the body as a whole. Unfortunately the water 

 load is not too accurately known in any of the animals represented ; 

 but there are additional data (in water deficits) to confirm the con- 

 clusion that presumed plasma decreases in volume by more than 

 its proportional share (Korth and Marx, '28; Keith, '22). The 

 volume of "erythrocytes" in circulation (CO), as measured inde- 

 pendently by carbon monoxide distribution, does not change ap- 

 preciably with water excess ; leaving the ''combined blood" volume 

 (Hb and CO) with less load than the whole body. The "extra- 

 cellular" volume (SCN) in deficit decreases somewhat more than 

 the average water load (AW). 



A favorite prediction would be that all volumes of distribution 

 increase and decrease in proportion to the body load of water. So 

 far no one volume is found exactly to fit this notion ; the data are 

 not extensive enough to decide for others than those here shown 

 and for Vd of bromide (Brodie et al., '39). 



There seems to be no doubt that most of the tissues whose incre- 

 ments of volume have been thus crudely measured, contain extra 

 water when the whole body has an excess, and are depleted of water 

 when the whole is in deficit. The modifications of water content in 

 some tissues are numerically equal to load of the whole, but in 

 other tissues are distinctly greater or less. Plainly the body's load 

 of water is unequally distributed through its parts. 



§ 79. Water contents (dilutions) of parts 



To avoid possible confusions, I separate the results based upon 

 volumes measured in a manner capable of determining absolute 

 quantities, from those in which changes of concentration are ascer- 

 tained. 



For these particular tests, excesses of water are produced 

 within 2 or 3 hours, a time too short to allow many chemical con- 

 tents of the body as a whole to change. The data are all obtained 

 between meals, and diet need not then enter the picture. On the 

 other hand, deficits of water are produced by partial privations last- 

 ing many days, as illustrated in the data of Falck and Scheffer 

 (1854b). Two young dogs of the same litter were analyzed (table 

 23, column 3), one at 76 days of age, the other at 104 days of which 

 the intervening 28 days were spent on a diet of dry "Zwiebach." 



