FOOD AND DIGESTION 45 



preceding. Translated into simple language this means 

 that we require for health lean meat (protein), fat meat, 

 (hydrocarbon or fat) and vegetables (starch and sugar), 

 with enough water to dissolve them after digestion and 

 carry the products of digestion to every part of the 

 body. 



Carbohydrates. Carbohydrates are, chemically, com- 

 pounds of carbon, hydrogen and oxygen, the last two 

 occurring in the proportions found in water. Thus glu- 

 cose (C 6 H 12 6 ) is composed of six elements of carbon, 

 twelve of hydrogen, and six of oxygen, which is practi- 

 cally the same as saying six elements of carbon in three 

 of water, which is composed of hydrogen two and oxy- 

 gen one (H 2 '0). There are various types of carbohy- 

 drates glucose, amylose but special attention need 

 here be called to none but glycogen which is the pecul- 

 iar form of starch formed in animals. 



Fats or Lipoids, are found, in varying amounts, in ani- 

 mal tissues, lying under the skin in large amounts, be- 

 tween the muscles, in the marrow of bones and in 

 smaller amounts in other situations. Fats, in the form 

 of oils, are found in many vegetables olive, cottonseed, 

 nuts, etc. Chemically, fats are compounds of glycerin 

 and a fatty acid. They are insoluble in water, and, be- 

 ing bad conductors, serve to keep the other tissues 

 warm. Normal fats belong to one of three types. 



Stearin, solid and melting only at comparatively high 

 temperatures. Mutton suet is a fine example of this type. 



Palmitin, is the principal constituent of most animal 

 and vegetable fats. It melts at a lower temperature 

 than stearin. 



Olein, always fluid except in low temperatures, is 

 found chiefly in vegetable fats, but occurs in that of 

 animals. 



