164 PHYSIOLOGY OP THE DOMESTIC ANIMALS. 



subject to variations dependent upon the mode of culture, the nature of 

 the soil, and the climate. They all contain a small amount of water and 

 cellulose in proportion to a large amount of solids (over 80 per cent.) in 

 which non-nitrogenous extractives and inorganic matters are in excess. 

 The following table gives their average composition : — 



In 100 parts. Wheat. Rye. Barley. Oats. Rice. Corn. 



Water .... 13.6 15.3 13.8 13.5 13.2 13.9 



Albumen 12.4 11.4 11.2 11.9 7.8 10.1 



Fat 1.7 1.7 2.1 5.8 0.7 4 8 



Carbo-hydrates and non- 

 nitrogenous extractive 



matters 67.9 67.8 65.5 57.5 76.4 66.8 



Cellulose 2.7 2.0 4.8 8.1 8 2.8 



Ash 1.7 1.8 2.6 3.2 1.1 1.7 



The cereal grains, of which wheat may be taken as a type, consist 

 of a number of layers arranged eccentrically. As many as seven different 

 layers have been recognized. Externally there is the external membrane 

 or epidermis; within that the epicarpium ; 3d, the endocarpium ; 4th, the 

 pigment-layer, or the testa, which in wheat is a reddish-brown membrane, 

 and gives to wheat-grains their characteristic color ; 5th, the tegmen, or 

 external nuclear membrane, below which are found a number of dice- 

 shaped cells (the perisperm), which were formerly spoken of as gluten- 

 cells, in which, however, the contents are mainly starch ; and it is within 

 the endosperm that the albuminous contents is contained between the 

 starchy granules. For, if a granule of wheat is divided and touched 

 with a drop of Millon's solution, it will be seen that the contents of the 

 endosperm only stain purple, while the shells and the so-called gluten- 

 cells remain unchanged. 



When wheat is subjected to the action of a digestive fluid the 

 albuminous bodies of the endosperm are dissolved and the starchy 

 granules become separated, while the hulls and so-called gluten-cells 

 remain entirely unaffected. The hulls contain a certain amount of 

 albuminous bodies, and are employed in bran and in black bread, and 

 have considerable nutritive value. In the so-called gluten-cells a ferment 

 seems to be present which has been called cerealiv, and which seems to 

 interfere in some way with digestion, and as a consequence, although 

 bran-bread is to a certain extent nutritious, it is yet difficult to digest. 

 In grinding, the external hulls or capsules are bursted and the contents 

 reduced to a fine powder in the mill, and thus become more digestible. 

 Hulls which are separated from the internal contents by milling always 

 contain a certain amount of albuminous matter and starch clinging to 

 them, so that even the chaff, or the hull or bran, contains considerable 

 amounts of nutritive matter, and may be used as fodder. Bran from 

 wheat has been found to contain 13 per cent, water, 14.5 per cent. 



