XIV. FOODS AND FEEDING 285 



Eventually, the various products are graded and sold as " patent 

 flour," "straight flour," "low grade or bakers' flour," "bran," 

 "shorts," "sharps" or "middlings" and "screenings". 



The proportions of these products vary somewhat, according to the 

 quality of grain used and the details of the milling, but in general, 

 100 parts by weight of uncleaned wheat yield about 



Screenings . 



Bran 



Shorts . 



Low grade flour . 

 "Patent" and straight flour 

 Loss (dust, etc.) . 



2-0 

 24-0 



2-0 



3-0 

 68-0 



1-0 



100-0 



Only the bran and shorts should, properly, be used as farm foods, 

 but often the screenings, containing much rubbish e.g., small stones, 

 mouse dung, weed seeds, fragments of straw and wood, and rust spores 

 together with refuse matter derived from the other sources than 

 wheat, are ground up and sold as bran. 



The bye-products from the milling of oats in the preparation of 

 oatmeal and groats, or of barley, in the preparation of pearl barley are 

 less important and less valuable, and consist largely of the outer husks. 



Hice bran and oat bran, indeed, are not really brans but consist of 

 the ground husks with some meal, and usually the germs. 



Eice polish, a finely divided material, is highly nitrogenous and 

 rich in phosphoric acid. 



From maize, various bye-products are obtained, both in the pro- 

 duction of " corn flour " and in the manufacture of starch and glucose. 



Maize bran is the husk or hull of Indian corn. 



Gluten meal is the highly nitrogenous portion of the grain which 

 lies immediately below the husk. 



Germ meal or cake is the nitrogenous and fatty residue left after 

 the expression of "corn oil " from the embryo of maize. 



Various other products, known as "gluten feed," "glucose meal," 

 "starch refuse," "starch feed," etc., largely sold in America, are also 

 obtained from maize. 



Digestibility of Foods. The value of a food depends not only 

 upon the quantities of its nutritious constituents, but also upon the 

 extent to which those constituents are actually utilised by the animals 

 which are fed upon it, or in other words upon the digestibility of its 

 nutrients. 



To determine this, direct experiments with animals have been made. 

 Such experiments consist in supplying known quantities of food to 

 animals and making careful determinations of the amounts of the 

 various food constituents present in the food and in the solid excrement 

 voided by the animal during the experimental period. 



Various precautions have to be taken in order to arrive at reliable 

 results, e.g., it is necessary to administer the food for several days before 

 the experiment really begins, in order to ensure the complete expulsion 

 of the residues from previous feeding. With the ruminants and horses, 



