32 cp:reals 



oxj'gt-n in nearly the wame proportions, — tire composition 

 of starch being carbon, six parts; hydrogen, ten; and oxygen, 

 five; as expressed by the formula CgHi„0,-; while for pure 

 glucose the formula is CoH,.0„. It will Ije noticed that 

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

 to say these elements are present in just the same ])ropor- 

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

 formula HX). A substance which is thus romi)osed of car- 

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

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

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

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

 stance known as ceUido-sc of which wood, cottfin, and paper 

 are mainly composed. Among the cei-eal grains, although 

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

 corn," th(> amount of digestible carl)ohydrate as given in the 

 tables may l)e understood as l)eing almost entireh" 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 sfTve (nther 

 for making fat or for giving warmth and strength. Since 

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

 solid insolulile particles, the necessity of somehow- converting 

 the 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 (_'i.jH.,„<)i,). This 

 being soluble in the sap of the young ])lant, ma}- Ix^ car- 

 ried to the regions of growth whiM'e food is iKH'ded. This 

 change of the insolulde starch into the soluble sugar is 

 accomplished through the action of a sul)stance calle(,l 

 diastase, one of a remarkable class of sul)stanc(^s known as 

 enzymes - that have the i:)ow(>r of bringing al_>out such changes 

 by their presence in comparatively minute amount. The 

 process of malting consists in causing grain to sprout and 

 allowing the conversion of starch to proccM^l until as much 



' Car-bo-hy'dratc < L. rarhri, coal; (!r. Iii/dar, water. 

 -En'zymc< C!r. ni, in; :iiiiii\ leaven; so called because actin.s like 

 the substance in leaven or yeast which jiroiluccs similar changes. 



