DIETETICS 629 



enous equilibrium, does not utilize at most more than 84 per cent. 

 Human milk contains about 2 per cent, of protein (mainly caseino- 

 gen), 3 per cent, of fat, 5 or 6 per cent, of carbo-hydrate (lactose or 

 milk-sugar), and from 0-2 to 0*3 per cent, of salts. Cow's milk 

 contains about 4 per cent, of protein, 4 to 6 per cent, of fat, 4 per 

 cent, of lactose, and 0*7 per cent, of salts. When given to infants it 

 should, as a general rule, be diluted with water, and some sugar 

 should be added to it. Ass's milk has about the same amount of 

 protein, lactose, and salts as human milk, but less than half as much 

 fat. It is very well borne and very completely absorbed. 



As to the place of water and inorganic salts in diet, it is neither 

 necessary nor practicable to lay down precise rules. In most well- 

 settled countries they cost little or nothing; very 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. When the food 

 is entirely animal, no additional salt is necessary. A 30-kilo dog 

 obtains in his diet of 500 grammes of lean meat only o -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 o -8 gramme sodium chloride. The Hereros in Damaraland, 

 who are physically one of the finest races in Africa, do not use salt 

 (Reclus). In this they resemble other tribes in different parts of 

 the world who eat no vegetable food, for example the Kirghiz, who 

 live on meat and milk, and the Todas, a pastoral tribe in Southern 

 India, who are ignorant of the use of vegetable foods and know 

 nothing of salt (McCay). Bunge has explained the difference 

 between the flesh and the vegetable feeder by showing 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 



