288 VETERINARY PHYSIOLOGY 



Occurrence of Carbohydrates. — In animals, except in 

 carnivora, carbohydrates form the chief source of energy 

 in the food, but only small amounts are present in the body. 



Glucose is present in blood to the extent of 0"1 to 0*15 

 per cent, usually. Lactose is present in milk ; glycogen in 

 the liver and muscles. 



In plants, carbohydrates occur in great variety, and form 

 the chief constituents. All the uionosaccharids, except 

 galactose, and disaccharids, except lactose, occur in solution 

 in plant juices. Those that are present in greatest amount 

 are glucose, fructose, and cane sugar. Starch is found in 

 large quantities as a reserve food in tubers and seeds, such as the 

 potato and in the common grains, and also in small quantities 

 in all green plants. The cell walls which form the frame- 

 work or skeleton of the plant is formed of cellulose. In 

 the young plant, the cell wall consists mainly of cellulose, 

 but as the plants increase in size, the framework is 

 made stronger by impregnating the cellulose of the cell 

 walls with hard tough substances. The chief of these is 

 lignin, which is a typical constituent of the woody parts of 

 plants. The older and larger the plant, the greater is the 

 amount of this fibrous material present. 



In the conventional analysis of food stuffs the carbo- 

 hydrates are divided into two groups. 



(1) "Nitrogen free extract." — This consists of those com- 

 pounds in solution, or which can be brought into solution 

 by the action of dilute acids or alkalies. This group 

 includes all the monosaccharids and disaccharids, and also 

 those polysaccharids like starch that can be hydrolysed to 

 the soluble form by these reagents. 



(2) "Crude Fibre-" — This includes all the remainder which 

 resist their reagents. Cellulose and lignin are typical, and 

 form the major part of the group. 



B. Not yielding Energy. 

 4. Ash (Inorganic Elements). 



Salts are present in all feeding stuffs, though in different 

 amounts and proportions. An ordinary mixed ration is 



