44 PHYSIOLOGY. 



for the maintenance of life. They need a more complex apparatus 

 for their transformation, and, as a consequence, the digestive organs 

 of the herbivora are better developed and more complex than those 

 of the carnivora. 



The cereals have the same general composition, all containing 

 the same proximate principles, but not all possess the same relative 

 amounts, because of which some are more valuable as food than 

 others. The most important of the cereals is wheat. 



Wheat, as a source of food, occupies a very important place and 

 is one of the most widely cultivated of the cereals. The wheat- 

 grains by grinding have their cellulose coats burst, and the resulting 

 powder is called flour. This contains, on an average, 70 per cent, of 

 'carbohydrates, 8 per cent, of proteid, and 1 per cent, of fat. The 

 coverings of the grain still contain some albumin and starch and 

 thus form bran, a substance used for feeding the herbivora. Bread is 

 made by a mixture of wheat-flour and water, forming dough. The 

 body which, on the addition of water, becomes viscid is called gluten, 

 and is a tough, sticky mass. This is made more porous by carbonic 

 acid, which is generated in the dough by the action of the yeast-plant 

 on sugar. The sugar is produced by the diastase in the flour, which 

 hydrates the starch into sugar. Baking kills the yeast-action and 

 makes the vesicles filled with carbonic acid expand, so the dough is 

 filled with little cavities. The crust of bread is formed by the heat 

 coagulating the gluten, and at the same time the heat transforms the 

 starch into dextrin and soluble starch. The glazing of the crust is 

 due to dextrin. The color of the crust and its taste are due to a 

 caramel generated by the action of heat on the sugar produced by the 

 diastase. 



ACCESSORY FOODS. 



In addition to the ordinary foods there is a series of articles 

 which are not necessary to the maintenance of life, but which are fre- 

 quently used. They are : alcohol, tea, coffee, and cocoa. Of these 

 accessory foods, alcohol is the predominant one and is used in a vari- 

 ety of drinks. 



Alcohol. Beer contains from 3 to 5 per cent, of alcohol. It 

 also has from 5 to 7 per cent, of extractives, which consist mainly of 

 dextrin and maltose, with albuminose, which give it nutrient proper- 

 ties. Each ounce usually holds about two cubic inches of carbon 

 dioxide. It is an infusion of malt fermented, to which a bitter prin- 

 ciple found in hops is added. It is frequently adulterated with sali- 



