INORGANIC FOODS. 191 



Eggs are also frequently used as food for calves and stallions when 

 rubbed up with the shells. To fattening calves three eggs may be admin- 

 istered daily, rubbed up, shells and all, with their daily supply of milk, 

 and serve to give an especially pleasant flavor to their flesh. For stallions, 

 ten to fifteen eggs may be given with their usual food. 



III. INOKGANIC FOODS. 



By inorganic foods are meant those inorganic compounds which 

 are found in the different tissues, secretions, and excretions of the 

 organism, which, being essential to the vital processes of the organism 

 and being continually removed, must be constantly replaced. Inorganic 

 substances are indispensable to a proper nourishment of animals, but 

 they are not usually taken in their simple form, but as constituents of 

 animal or vegetable matter, or in the fluids which are drunk. Of the 

 inorganic foods, water, common salt, salts of lime and potassium, and 

 iron are indispensable, as they are the necessar}- constituents of the 

 blood, lymph, bones, and different tissues, and are continually being 

 removed in the nutritive processes of the economy. 



1. Water. — Water, as an alimentary principle, is taken into the 

 system, either alone as a drink, or in combination with articles of food ; 

 in both of which cases it is also associated with a certain amount of 

 inorganic salts, as animals, unless pressed by great thirst, will refuse to 

 drink distilled water. For certain animals, such as rabbits and kangaroos, 

 which seldom or never apparently drink water, enough fluid for their 

 needs is contained in the succulent vegetables which serve as their 

 food; for if rabbits, for example, are fed on dry food, such as bran, they 

 will then require water, and will drink it like other animals. So also 

 sheep, which, as a rule, require but small amounts of water because 

 of the succulent character of their food, if in dry localities, or if 

 they are fed on dry food, will also hunt for water, like other animals 

 susceptible of thirst. Water not only carries into the system materials 

 capable of solution, but it holds matters in suspension which in some 

 cases may be nutritious, in others poisonous. The piu-est water is not 

 necessarily the best for animals or man, nor is dirty water necessarily 

 injurious. Drinking-water must possess certain qualities. It must be 

 fresh, clear, without odor, and of a certain taste. It should always con- 

 tain gases and mineral matter in solution, but be free from organic- 

 substances. The presence of the latter, which are always injurious, may 

 be recognized by the addition of a small amount of potassium perman- 

 ganate solution to the suspected water, when, if organic substances are 

 present, the bright-purple solution will become a dirty brown. Drinkable 

 water should contain from 20 to 30 per cent, of its volume of air in 



