NON-NITROGENOUS NUTRIENTS. 87 



som, are bruised and mascerated, and the liquid then 

 pressed out, a large portion of the starch will pass with the 

 juice from the vegetable tissue, and after standing for a 

 short time, will settle as a mealy mass. Almost every 

 housewife knows how to separate starch from potatoes. 



It cannot be dissolved in cold water without the grains 

 are mashed very fine, and then only a small proportion is 

 dissolved. But when mixed with water at the boiling 

 point, the grains absorb water and burst. It is from this 

 fact that cooking starchy food is supposed to render it 

 much more digestible. When boiled with weak acids or 

 alkalies it is converted into grape sugar, even the action of 

 saliva is supposed to change starch into sugar. Liebig 

 supposed it turned into sugar in the process of digestion. 

 We shall give its composition with other carbo-hydrates. 



Dextrine. This may be considered as an artificial pro- 

 duct of starch, produced by dry heat upon it. It is a com- 

 mercial article under the name of British gum. 



Sugars. There are cane, grape and fruit sugars. The 

 first is produced from the juice of the sugar cane plant, 

 from beet root, sugar-maple and other plants this is the 

 principal sugar of commerce. Grape sugar and fruit sugar 

 occur in the juices of many plants, and are often found 

 together and in the fruits and honey. They are all soluble 

 in water, and easily digested. In the process of digestion, 

 cellulose and starch are supposed to be turned into sugar. 



THE PECTIN SUBSTANCES. These are found in fruits and 

 roots. In fruits these substances form jellies, but their ex- 

 act chemical composition has not been much investigated. 

 It has been supposed by some careful observers that the 

 pectin of fruits and of turnips, beets, carrots and other 

 roots, has an important effect in assisting in the digestion 

 of other food, that this substance assists in rendering other 



