344 HUMAN PHYSIOLOGY 



individuals must receive a moderate quantity even 

 though they aim to avoid it; it is represented in most 

 foods. The bulk of the salt which we eat is taken to 

 improve the flavor of various dishes, but a certain amount 

 seems to be a more fundamental necessity. 



World-wide observation has shown that salt is gen- 

 erally prized by the vegetarian races but disliked by 

 those that are approximately carnivorous. The animals 

 which seem to crave it are herbivorous, cattle, sheep, 

 and deer being among them. Cats and dogs show an 

 aversion to meat that is noticeably salt. An explanation 

 of these divergent instincts has been offered which is 

 ingenious and apparently reasonable. 



Salts of sodium and potassium are mingled in natural 

 foods. In most cases the potassium compounds are 

 in excess, but sometimes their preponderance is only 

 moderate, while in other cases it is overwhelming. In 

 meat the potassium does not so greatly exceed the sodium 

 as it does in most vegetables. Potatoes, for example, 

 are very rich in potassium and poor in sodium. It is 

 argued that if the system is loaded with a, large quantity 

 of potassium salts the duty of restoring the composition 

 of the blood to the normal standard must fall upon the 

 kidneys. These organs will soon eliminate the surplus 

 potassium, but while they are doing it they will let slip 

 more or less of the abundant sodium chlorid of the 

 plasma. A definite need for this salt will then arise. 



An investigator has shown that eating much potas- 

 sium has just the effect assumed. Experimenting upon 

 himself he swallowed salts of potassium until he had 

 taken on a single day the equivalent of 18 grams of 

 potassium oxide. All this soon passed into the urine, 

 but there was lost with it 7 grams of sodium chlorid 

 for which the diet made no compensation. The total 

 potassium intake in this experiment seems large, but it 

 was not greater than might be ingested in a day by one 

 living chiefly upon potatoes. 



Stefansson, the Arctic traveller, has remarked the 



