AGRICULTURAL CHEMISTRY. 123 



portant ingredient of bread, being formed in the loaf by the process 

 of baking, from the transformation of starch. 



Gum is a generic term, and includes a number of substances, as 

 gum tragacanth, gum Arabic, gum Senegal, cherry gum, &c, which, 

 though unlike in some respects, agree in composition, and have the 

 property either of dissolving or swelling up in water with the forma- 

 tion of an adhesive mucilage or paste. In the bread grains there is 

 usually found a small quantity of gum soluble in water, and in meal 

 from the seed of millet it has been observed to the amount of 10 

 per cent. 



The sugars are so familiar that they scarcely require special notice. 

 Cane sugar or sucrose is the intensely sweet soluble crystallizable 

 principle found in the juice of the cane, maple, and sugar beet, It 

 is found, besides, in many other plants. 



Fruit sugar or fructose is uncrystallizable, and exists in the juice 

 of acid fruits, in honey and in the bread grains. 



Grape sugar or glucose is found solid and crystallized in dried fruits, 

 especially in the grape. It gradually separates from honey as the 

 latter candies. 



In the young cell this group of bodies is represented by cellulose, 

 as the cell wall, and by dextrin and the sugars existing in its fluid 

 contents. 



The machinery of the vegetable organism, which all the while 

 operates as perfectly in the single cell as in the complex mass of cells, 

 has the power to transform most if not all these bodies into every 

 other one, and we find them all in every individual of the higher 

 orders of plants — at least in some stage of its growth. From dex- 

 trin, which is dissolved in the juice of a parent cell, is moulded the 

 cellulose which envelopes a new cell. 



From starch, and perhaps cellulose in the stem of the maple, cane 

 sugar is formed in the changeful temperature of spring, and, as the 

 buds swell, this sugar is reorganized again into cellulose and starch. 

 The analysis of the cereal grains oftentimes reveals the presence 

 of dextrin, but no sugar or gum; while at other times the latter are 

 found, but not the former. 



It is easy to imitate many of these transformations outside of the 

 vegetable organism. By the agency of heat, acids, and ferments, 

 either singly or jointly, we may effect a number of remarkable 

 changes. 



Cellulose and starch are converted, first, into dextrin, and finally 

 into grape sugar, by boiling with a dilute acid. In this way glucose 

 is largely manufactured from potato starch, and has, in fact, been 

 made from saw-dust. This transformation is also effected by the 

 digestive apparatus of herbivorous animals, and in case of starch by 

 a roasting or baking heat, So, too, in the sprouting of seed, the same 

 changes occur, as exemplified in the preparation of malt. 



By heat and acids inulin is also converted into a kind of sugar, but 

 without the intermediate formation of dextrin. The same is true of 

 the gums. By these agencies cane sugar is converted into fruit 

 sugar, and this spontaneously passes into grape sugar. 



