MINERAL METABOLISM 



313 







that the water lost on profuse sweating is much more rapidly regained on 

 a salt-rich than on a salt-poor diet, when water and food intake are other- 

 wise unchanged. They hold that the largo amount of dilute urine follow- 

 ing muscular exertion is due to the thirst which prompts water drinking 

 and since no salt is taken with the water it cannot he incorporated .into 

 the body. The fact that thirst is only transitorily slaked by water drink- 

 ing under such conditions is also a result of the lack of NaCl. 



Working from the other direction Belli reduced his NaCl intake to 

 a minimum during 10 days of a metabolism experiment which consisted 

 of 4 days preliminary period (10.2 g. NaCl daily) 10 days salt-poor 

 (1.03 g.) and 3 days final (9.32 g.). His decreased water intake during 

 period II (2000 g.) was enough to account for his loss of weight (1.3 kg. ) 

 since water excretion was practically unchanged, and in the final period 

 he^apidly regained weight with water balances as follows : 



During period II the urinary Cl fell to 0.04 per cent and in the last five 

 days there was Cl equilibrium. Klein and Verson in 1867 found a similar 

 loss of weight in a period without salt and in the following period a large 

 gain which they ascribed to water retention. 



In experimental work on a diet free from all mineral constituents 

 similar losses of weight have been followed by a rapid gain, in one case 

 4.1 kg. in 72 hours, on a return to a normal diet or on the addition of 

 only lS T aCl (Taylor(&) ; Goodall and Joslin). 



There is apparently no continuous storage of NaCI in the body, an 

 increased intake may result in slight retention for a few days, but equilib- 

 rium is soon established on the higher level. In work on dogs v. Hoesslin 

 established that on an intake sufficient to exceed the minimum needs all 

 the ingested NaCl was eliminated by the kidney, not equally on all days 

 but with daily and periodic variations. On a quantity of salt much ex- 

 ceeding the minimum needs there was likewise equilibrium over a long 

 period, but from day to day the capacity of the organism for water and 

 salt varied within limits which were about 10 per cent each way from the 

 average. The water content of the feces is less the greater the salt intake, 

 Cl and water secretion by the kidney run approximately parallel. 



Urinary elimination of Cl undergoes a rapid rise upon ingestion of 

 food (Dobrovici; Hermannsdorfer), due to absorption of NaCl by the 

 stomach, followed by a fall representing secretion of HC1 in the gastric 

 juice, which is accompanied by increased alkalinity of the blood (Van 



