32 CEREALS 



oxygen in nearly the same proportions, — the composition 

 of starch being carbon, six parts; hy(h'ogen, ten; and oxygen, 

 five; as expressed liy the fornuihi C,;Hi„0-; while for pure 

 glucose the formula is C,;Hi.X),,. It will be noticed that 

 in each there is twice as much hydrogen as oxygen; that is 

 to say these elements are present in just the same propor- 

 tion as in water, which, as is well known, has the chemical 

 formula HoO. A substance which is thus composed of car- 

 bon united with the elements of water is called a carbohy- 

 drate.^ Not only do starch and glucose come under this 

 head, but also other kinds of sugar, various sorts of true gum 

 (such for example as that on postage stamps), and the sub- 

 stance knowm as cellulose of which wood, cotton, and paper 

 are mainly composed. Among the cereal grains, although 

 sugar is sometimes present to a notable degree, as in "sweet 

 corn," the amount of digestible carbohydrate as given in the 

 tables may be understood as being almost entirely starch. 



During the process of digestion in man and other animals 

 starch is converted into sugar, and as such is absorbed into 

 the blood and carried all over the system to serve either 

 for making fat or for giving warmth and strength. Since 

 only fluids can l)e absorbed, and since starch is composed of 

 solid insoluble particles, the necessity of somehow converting 

 tlie starch of our food into sugar, is obvious. 



Similarly, when grains sprout, the starch in them under- 

 goes a sort of digestion and becomes converted into sugar, 

 largely maltose or "malt sugar" (formula CioH.oOn)- This 

 being soluble in the sap of the young plant, may be car- 

 ried to the regions of growth where food is needed. This 

 change of the insoluble starch into the soluble sugar is 

 accomplished through the action of a substance called 

 diastase, one of a remarkable class of substances known as 

 enzymes - that have the power of bringing about such changes 

 by their presence in comj^aratively minute amount. The 

 process of malting consists in causing grain to sj^rout and 

 allowing the conversion of starch to proceed until as much 



' Car-bo-hy'drate < L. carbo, coal; Gr. hydor, water. 

 -En'zyme<; Gr. en, in; zi/nic, leaven; so called because acting like 

 the substance in leaven or yeast which produces similar changes. 



