Of the chemical processes which occur in plants very little is known. Few halting-places between raw materials and finished products can be marked. The final products are sugars and starches, oils, proteins, and a vast number of other substances—alkaloids, glucosides, etc. Condensation, dehydration, and deoxidation are the methods by which the synthesis of these compounds is accomplished. These methods are adopted simultaneously in varying degree. The large group of bodies known as sugars and starches are, with few exceptions, built on the C₆H₆ model; in fruit-sugar, C₆H₁₂O₆, six atoms of carbon are linked to one another and to six molecules of water. The formula of starch is (C₆H₁₀O₅)ₙ. Not only has water been removed from the molecule, but an unknown number of molecules have been linked together. This condensation and dehydration is effected whenever sugar carried in cell-sap is deposited as starch in seeds or tubers. These compounds are hexatomic. The chemist pictures them as made by the union in the first place of six atoms. As small drops unite to form larger ones, so small molecules, under the direction of the protoplasm of plants, close together. The reactions which characterize animal protoplasm are of a different kind. They belong to the descending series. Close molecules are unfolded. Water is incorporated with them. Hydrogen and carbon are oxidized into water and carbonic acid. The conversion into sugar of glycogen or of starch may be taken as an illustration of expansion. Starch, (C₆H₁₀O₅)ₙ, becomes maltose, C₁₂H₂₂O₁₁, and then dextrose, C₆H₁₂O₆. The grouped molecule of starch opens out. The breaking of the double molecule of maltose into two molecules of dextrose is a further illustration of progress towards simplicity. Hydration, union with H₂O, accompanies this expansion. Hydrolysis is the secret of almost all digestive acts. Starch is hydrolysed into sugar, fat hydrolysed into glycerin and fatty acid, proteins hydrolysed into peptones.