114 FOOD. 



he becomes exhausted, and feels the deficiency in a marked degree. 

 Magendie found, in his experiments on dogs subjected to inanition, 1 that 

 if the animals were supplied with water alone they lived six, eight, and 

 even ten days longer than if deprived at the same time of both 

 solid and liquid food. Sodium chloride, also, is usually added to the 

 food in considerable quantity, and requires to be supplied as a condi- 

 ment with tolerable regularity ; while the remaining inorganic materials, 

 such as the calcareous salts, and the alkaline phosphates and sulphates, 

 occur naturally in sufficient quantity in most of the articles used as 

 food. 



The entire quantity of mineral substances discharged daily by a 

 healthy adult, by both the urine and perspiration, averages as follows : 



QUANTITY OF MINERAL MATTERS DISCHARGED PER DAY. 



Sodium and potassium chlorides 15.0 grammes. 



Calcareous and magnesian phosphates .... 1.0 " 

 Sodium and potassium phosphates . , . 4.5 " 



Sodium and potassium sulphates 4.0 " 



24.5 " 



According to the average dietaries for adults in full health collected 

 by Dr. Playfair 2 about 20 grammes of mineral matter are daily intro- 

 duced with the food. The remainder is to be accounted for by the 

 phosphates and sulphates formed within the system as above described. 



Non-Nitrogenous Organic Ingredients of the Pood. 



These substances, so far as they enter into the composition of the 

 food, are divided into the two natural groups already mentioned 

 namely, the carbohydrates, including starch and sugar, and the fats, 

 including all the varieties of oleaginous matter. Since starch is always 

 converted into glucose in the digestive process, these two substances 

 have the same value and significance as nutritive materials. As the 

 carbohydrates are to be found as a general rule only in vegetable pro- 

 ducts, they do not constitute a part of the food of carnivorous animals. 

 It is true that glucose exists in the milk even of the carnivora during 

 lactation, and is consequently supplied as a nutritive material to the 

 young animal during the early portion of its growth. But this supply 

 ceases as soon as the period of lactation is finished ; and the fact of the 

 secretion of sugar by the mammary gland, as well as that of its produc- 

 tion in the liver, shows that in the carnivorous animal the carbohydrates 

 requisite for the process of nutrition may originate within the body from 

 other organic substances. This does not apply, however, to the vege- 

 table feeders or to man. The carnivora have no desire for vegetable 

 food, while the herbivora live upon it exclusively, and in man there is 

 a natural craving for it, which is almost universal. It may be dis- 



1 Comptes Rendus de l'Acadmie des Sciences. Paris, tome xiii. p. 256. 



2 London Chemical News, May 12, 1865. 



