CORRELATIVES OF WATER CONTENT 211 



Hence factors of growth in size, diet, time, age and constitution 

 entered into the differences of the two individuals. Each dog was 

 killed, its organs were excised and weighed, and the proportion of 

 water in each organ was ascertained by a particular analytical 

 procedure of drying. The changes of body weight and therefore 

 of total water load (AW = -21) between "control" and "desic- 

 cated" are known; what is the change in each portion of the body? 

 First it is necessary to decide how the analyzed water contents 

 of the same tissue in each of the two individuals shall be compared. 

 The data known are: wet weight (F), dry weight (D) and water 

 weight (E = F-D). The ratio E/F is tabulated by Falck and 

 Scheffer ; but F is itself changing with water privation. The known 

 fraction that is believed to change little or none is D ; or, compara- 

 ble samples of tissues are those in which Di = Do. Hence the ratio 

 E/D is the basis of comparisons ; in order to make its increments 

 comparable to increments of body water (AW) as first defined, it 

 may be corrected to fresh weight and % of Fo by multiplying by 

 100 Eo/Fo. 



100Eo/E,_Eo\/Eo_ /B\Do \_ 



Fo U Wo)iw,-^^^[F,i)rV-^^ 



This is the amount of water added to or lost from 100 units of 

 original weight. The increment is all water, however much non- 

 aqueous weight may be included in Fo. 



The ratio AE has the same dimensions as AW and AV, for in both 

 cases the water lost or gained is in per cent of the unit analyzed. 

 Since AE may be of many types, the type of measurement from 

 which AE is derived is more specifically designated by the abbrevi- 

 ation A/D, or dilution of dry substance. Both measures, AV (== AW 

 in this case) and AE, can be compared for the whole animals of 

 Falck and Scheffer (1854b) : 



AV = AF/Fo = -^^^^^^ = -20.78%ofFo(orofBointhiscase) 

 3178.72 gm. / u v u / 



AE = A/D = -2p^^ = - 17.39% of Fo (or of Bo in this case) 



The comparison indicates that the dog deprived of water lost non- 

 volatile materials too, and the two measures of water loss differ 

 (by 18 per cent of their mean). A similar comparison may be 

 made for each tissue mass as weighed and as analyzed (table 23, 

 columns 2 and 3). 



Measurements of dilution are not limited to analyses by volatili- 



