550 A MANUAL OF PHYSIOLOGY 



different quantities can be taken and excreted without harm ; 

 and both economics and physiology may well leave every man 

 to his taste in the matter. Salt is indeed for the most part used, 

 not as a special article of diet, but as a condiment to give a 

 relish to the food, just as a great deal more water than is actually 

 needed is often drunk in the form of beverages. It is certain 

 that the quantity of salt required, in addition to the salts of the 

 food, to keep the inorganic constituents of the body at their 

 normal amount, is very small. A 30-kilo dog obtains in his diet 

 of 500 grammes of lean meat only 0*6 gramme sodium chloride, 

 and needs no more. An infant in a litre of its mother's milk, 

 which is a sufficient diet for it at six to nine months, gets only 

 0-8 gramme sodium chloride. Bunge, however, has shown that the 

 proportion of potassium and sodium salts in the food is a factor in 

 determining the quantity of sodium chloride required. A double 

 decomposition takes place in the body between potassium 

 phosphate and sodium chloride, potassium chloride and sodium 

 phosphate being formed and excreted ; and the loss of sodium 

 and chlorine in this way depends on the relative proportions 

 of potassium and sodium in the food. In most vegetables the 

 proportion of potassium to sodium is much greater than in 

 animal food, so that vegetable-feeding animals and men as a 

 rule desire and need relatively great quantities of sodium chloride. 

 But it is stated that the inhabitants of a portion of the Soudan 

 use potassium chloride instead of sodium chloride, obtaining 

 the potassium salt by burning certain plants which leave an ash 

 poor in carbonates, and then extracting the residue with water 

 and evaporating (Dybowski). A beef-eating English soldier in 

 India consumes about 7 grammes (J oz.), a vegetarian Sepoy 

 about 18 grammes (f oz.), of common salt per day. 



Wine, beer, tea, coffee, cocoa, etc., belong to the important 

 class of stimulants. Some of them contain small quantities 

 of food substances, but these are of secondary interest. In beer, 

 for example, there are not inconsiderable amounts of proteins, 

 dextrin, and sugar. But 14 litres of beer would be required to 

 yield 15 grammes nitrogen, and 10 litres to give 250 grammes 

 carbon ; and nobody, except a German corps student, could 

 consume such quantities. The minimum nitrogen require- 

 ment, however, as well as the necessary heat value, could 

 theoretically be covered by 6 or 7 litres of good German 

 beer. 



In some cocoas there is as much as 50 per cent, of fat, 4 per 

 cent, of starch, and 13 per cent, of proteins ; and in the cheaper 

 cocoas much starch is added. Still, a large quantity of the 

 ordinary infusion would be needed for a satisfying meal. 

 Frederick the Great, indeed, in some of his famous marches 



