60 THE CHEMISTKY OF FOOD. 



and the palm, this kind of food may be obtained from 

 vegetable sources in abundant quantities. 



23. The Sugars, or the Saccharine Substances. 

 These constitute the third, and last, group of the organic 

 substances, which are employed as food. This group em- 

 braces, in addition to the different kinds of Sugar, the 

 varieties of starch and gum, from whatever source derived. 

 The two substances last named do not, at first sight, pre- 

 sent many points of similarity to sugar ; but they closely 

 resemble it in respect to their ultimate chemical composi- 

 tion, being made up of the same elements, in nearly the 

 same proportions. And their office in the system is the 

 same, since they are all changed into sugar by the processes 

 of digestion. 



* 24. Sugar is chiefly of vegetable origin; the animal 

 varieties being obtained from honey and milk. The most 

 noticeable characteristic of this substance is its agreeable, 

 sweet taste, which makes it everywhere a favorite article of 

 food. But this quality of sweetness is not possessed by all 

 the varieties of sugar in the same degree ; that obtained 

 from milk, for instance, has a comparatively feeble taste, 

 but rather imparts a gritty feeling to the tongue. The 

 other important properties of sugar are, its power to 

 crystallize when evaporated from watery solutions, such as 

 the juices of many plants ; a tendency to ferment, by which 

 process alcohol is produced; and a ready solubility in 

 water. This latter quality renders it very easy of digestion, 

 and more so than any other of the saccharine, group. It is 

 computed that the annual production of sugar, in all parts 

 of the world, is more than one million of tons. The kind 

 of sugar that is in ordinary use, in this country, is prepared 

 from the juice of the sugar-cane, which contains eighteen 

 per cent, of sugar. In France it is manufactured from the 



23. Which are the third of the organic groups? What do they embrace? 

 Points of resemblance ? 



24. Origin of the sugars? Ordinary eugar? Beetroot? Maple-sugar? Grape- 

 r-ugar? Cane-sugar? 



