The Constituents and Uses of Food. 



The chemical expression for starch and dextrin is n (CgHioOJ, 

 a formula which corresponds to the following percentages : — 

 Carbon 44 "4, Hydrogen 6 "2, Oxygen 49'4. 



The term "sugar" is commonly applied to a number of 

 different, although related substance's, possessing a more or less 

 marked sweet taste. These substances are arranged by chemists 

 in three groups, of which cane-sugar, grape-sugar, and manna- 

 sugar may be taken as the respective types. 



Group i. — The chemical formula for the sugars of the first 

 group is CjjH^^O^, an expression which corresponds to the 

 following percentages: — Carbon 42T, Hydrogen 6"4, Oxygen 5i"5. 



a. Cane-sugar occurs in the sugar-cane [Saccharum officina- 

 rum) and in many other grasses ; in some palms, as Borassus 

 flabelliformis, Caryota urens, and Arenga saccharifera ; in beet- 

 root [Beta vulgaris) ; in the carrot [Daucus Carota) ; the parsnip 

 {Pastinaca sativd) ; in some maples, as Acer saccharinum and 

 three other North American species ; and in the nectaries of 

 many flowers. 



b. Milk-sugar has been found in the latex of Achras Sapota. 



c. Melitose occurs in the manna exuding from many species 

 of Eucalyptus. 



d. Melezitose is found in the "manna" which exudes from 

 the young twigs of the larch ; it is the chief constituent of 

 " Lahore Manna," from the Camelthorn, Alhagi maurorum 

 {Hedysarum alkagi, L.), a shrub growing in Persia and Afghanistan. 



e. Mycose occurs in "trehala manna," known in Persia as 

 " nest -sugar ; " it is also a constituent of several fungi. 



/ Maltose occurs naturally to a small extent in many cereal 

 grains, and more abundantly in malt. 



Group ii.— The chemical formula for the sugars of the 

 second group is C^HgOg, an expression which corresponds 

 to the following percentages : — Carbon 40-0, Hydrogen 67, 

 Oxygen 53-3. 



a. Dextrose, or grape-sugar, is the hard crystalline sugar so 

 abundant in raisins ; it is found in ripe cherries, and, associated 

 with another glucose, in honey and in many immature fruits. 



