The digestion of starch--which is insoluble in cold water--really begins with the cooking, which by softening the outer coating or fibre of the grains, causes them to swell and burst, thereby preparing them for the chemical change which is caused by the action of the saliva in converting the starch into a species of sugar before it enters the stomach. Substances which are insoluble in cold water cannot be absorbed into the blood, therefore are not of any value as food until they have become changed, and made soluble, which overtaxes the digestive organs and causes trouble. The temperature of the saliva is too low to dissolve the starch fibre unaided. Each of the digestive juices has its own work to do, and the saliva acts directly upon the starchy food; hence the importance of thoroughly masticating such food as bread, potatoes, rice, cereals, etc. The action of heat, in baking, which causes the vapor to rise, and forms the crust of starchy food, produces what is called dextrine, or partially digested starch. Dextrine is soluble in cold water, hence the ease with which crust and toast--when properly made--are digested. It is more important to thoroughly chew starchy food than meat, as it is mixed with another digestive juice, which acts upon it in the stomach. Sugars. SUGAR. There are many varieties of sugar in common use, viz.: cane sugar, grape sugar or glucose, and sugar of milk (lactose). As food, sugars have practically the same use as starch; sugar, owing to its solubility, taxes the digestive organs very little. Over-indulgence in sugar, however, tends to cause various disorders of assimilation and nutrition. Sugar is also very fattening, it is a force producer, and can be used with greater safety by those engaged in active muscular work. Cane sugar is the clarified and crystallized juice of the sugar cane. Nearly half the sugar used in the world comes from sugar cane, the other half from beet roots. The latter is not quite so sweet as the cane sugar. Sugar is also made from the sap of the maple tree, but this is considered more of a luxury; consequently, not generally used for cooking purposes. MOLASSES AND TREACLE. Molasses and treacle are formed in the process of crystallizing and refining sugar. Treacle is the waste drained from moulds used in refining sugar, and usually contains more or less dirt. GLUCOSE. Glucose, or grape sugar, is commonly manufactured from starch. It is found in almost all the sweeter varieties of fruit. It is not so desirable for general use as cane sugar. HONEY. Honey is a form of sugar gathered by bees from the nectar of flowering plants, and stored by them in cells. Honey contains water 16.13, fruit sugar 78.74, cane sugar 2.69, nitrogenous matter 1.29, mineral matter 0.12 per cent. (Konig.) Grains.