I42 STORRS AGRICULTURAL EXPERIMENT STATION. 
wheat. Besides the albuminoids proper, there are other nitro- 
genous compounds present in vegetable substances, such as the 
amides, which are less valuable for feeding purposes get are the 
true albuminoids. 
The fat, or, more properly speaking, the ‘ether extract,” 
includes a large class of compounds dissolved by ether in the 
analyses made in the laboratory. In addition to the fats or oils 
proper, the ether extract may contain wax,-resins, chlorophyl 
(the green coloring matter of plants), besides several other less 
familiar compounds. 
The carbohydrates include both the fiber and the “‘nitrogen- 
free extract.” Fiber is the woody part of a plant, consisting prin- 
cipally of cellulose and lignin. Cellulose is the digestible part 
of the fiber and is much like starch in its chemical composition | 
and probable feeding value. 
' The nitrogen-free extract is not directly determined in ordi- 
nary analyses, but is found by difference; that is, by subtracting 
the sum of the percentages of the other ingredients from one 
hundred per cent. It consists of starch, sugar, gums, and many 
other substances not so well known. 
All the parts of plants contain more or less mineral matter or 
ash, and generally in more than sufficient amount for feeding 
purposes, and for this reason it is not usually taken into account 
in calculating rations. It is, however, of the utmost importance 
in the proper nutrition of an animal that the ash constituents be 
furnished in sufficient quantity. 
USES OF THE FOOD. 
The food supplies the needs of the body in several ways. It 
is used to form new tissues and fluids and to repair the wastes of 
the old; it is stored in the body in the form of fat; and it is con- 
sumed as fuel, its potential energy being erinerepnen into heat 
or muscular energy, or other forms of energy required by the 
body. 
It is only recently that we have learned to know in what way 
the various classes of nutrients of which the food materials are 
composed, are used in the body. While there is much that 
remains to be done before we shall have an exact knowledge of 
this subject, the following statements can be made with consider- 
able certainty: 
The protein forms tissues, as muscles, tendon, etc., and fat, and 
serves as fuel. 
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