RELATION OF FOOD TO NUTRIMENT. 269 



able kingdom, for no animal has the physiological power of 

 combining mineral elements so as to form them into food. But the 

 vegetable assimilates inorganic materials under the influence of light, 

 storing up in itself various elements, in different combinations, 

 essential to the formation and nutriment of vegetable and animal 

 structures. So, without taking much inorganic matter directly into 

 the system, we obtain what is necessary through its presence in the 

 organic. 



In popular language, what is taken into the system is termed 

 "food" and " drink;" the former including solid, the latter liquid 

 matter. But, convenient as these designations may be, they do not 

 accurately represent the facts of the case. Milk, for instance, is very 

 rich in solids, while nine-tenths of the component parts of turnips con- 

 sist of water. A better classification, therefore, is to arrange all food 

 whether liquid or solid, into organic and inorganic portions the 

 organic comprising those elements which are combined and pro- 

 duced only through the agency of some living structure, whether 

 vegetable or animal, and the inorganic those which are derived 

 directly from the mineral kingdom. Water and salt are inorganic. 



In view of their chemical composition, organic foods are 

 generally classified as nitrogenous and non-nitrogenous. The nitrog- 

 enous consist of carbon, oxygen, hydrogen and nitrogen, in differ- 

 ent proportions, with generally the addition of sulphur and phos- 

 phorus. The non-nitrogenous consist of only the first three 

 ingredients. 



Nitrogenous Food It will be observed that the presence 

 or absence of nitrogen constitutes the chief difference between these 

 classes; and as it enters very largely into the composition of the 

 body, an abundant supply of it is essential. Some may suppose 

 that, as this is an important constituent of the atmosphere four- 

 fifths of which are nitrogen, it might be imbibed from the air; 

 but it is not. It is derived from the food and must be introduced 

 into the system in combination with other organic elements. 



Among nitrogenous foods the flesh or muscular tissue of ani- 

 mals contains the elements which are required for forming flesh 

 and generating heat. Hence life could be maintained for a consid- 

 erable time on animal food alone. Bread, among vegetable foods, 

 also contains nearly all the elements required for nutrition. 



Nitrogenous foods must all undergo the process of digestion 

 before they can be assimilated and form part of the body. This 

 process is really one of comminution and liquefaction. The food 

 is reduced to a finely divided state by the action of the teeth, the 

 muscles of the mouth and the saliva; when it reaches the stomach 

 it is further disintegrated by the action of the gastric juice, with 

 which it is brought into contact by the motion of this organ. 

 Thence it passes out in a state of fluidity, as a very soluble and 

 diffusible product called chyme, and easily transmitted to the blood- 

 vessels. The food has now lost its characteristic properties, but 



