118 THE HUMAN BODY. 



in the alimentary canal. Beeswax, on the other hand, is a 

 fat which will not melt in the intestines and so passes on 

 unabsorbed, although from its composition it would be use- 

 ful as a food could it be digested. 



Carbohydrates. These are mainly of vegetable origin. 

 The most important are starch, found in nearly all vege- 

 table foods; dextrin; gums; grape sugar (found in most 

 fruits) ; and cane sugar. Sugar of milk and glycogen are 

 alimentary principles of this group derived from animals. 

 All carbohydrates, like the fats, consist of carbon, hydrogen, 

 and oxygen; but the percentage of oxygen in them is much 

 higher than in fats. When oxidized they have therefore less 

 power of combining with additional oxygen than fats, and 

 so are not capable of yielding as much energy to the body. 



Inorganic Foods. The most important of these are 

 water; common salt; and the chlorides, phosphates, and 

 sulphates, of potassium, magnesium, and calcium. A suf- 

 ficient quantity of most of these substances, or of the ma- 

 terial for their formation, exists in all ordinary articles of 

 diet, so that we do not swallow most of them in a separate 

 form. Water and table salt form exceptions to the rule 

 that inorganic bodies are eaten imperceptibly along with 

 other things, since the body loses more of each daily than is 

 usually supplied in that way. It has been maintained that 

 salt as a separate article of diet is an unnecessary luxury, 

 and there seems to be some evidence that certain savage tribes 

 live without more than they get in the meat and vegetables 



What is the chief source of carbohydrates? Name the most im 

 portant. Name carbohydrate foods derived from animals. How do 

 they resemble fats in composition, and how do they differ from them? 

 Can an ounce of starch yield as much energy to the body as an ounce 

 of fat? Give a reason tor your answer. 



Name the more important inorganic foods. Why do we not require 

 to eat most of them separately? What inorganic foods are taken in 

 a separate form ? Why ? 



