CONSTRUCTIVE PROCESSES 35 



enzyme into soluble carbohydrates glucose, laevu- 

 lose, or maltose ; the route is determined by the 

 demand for them, and the mode of distribution is 

 by diffusion. Where a tuber begins to sprout the 

 starch is drawn upon for constructive purposes, 

 and, being converted to sugar, travels to the growing 

 points of the young shoots, and supplies a large 

 portion of the plastic material necessary for growth. 

 Sugar is formed by the hydrolysis of carbohydrates 

 by acids or alkalies. Hydrolysis by alkalies is due 

 to the presence and influence of OH ions ; hydrolysis 

 by acids to free H ions ; the former is a slow, the 

 latter a comparatively rapid process.* In the con- 

 version of starch to sugar by ptyalin, or other 

 cellular enzyme, the hydrolysis is probably per- 

 formed by ionisation in a similar manner. Inulin is 

 not converted to sugar by enzymes such as ptyalin 

 or amylopsin, and, when consumed by animals, its 

 conversion takes place in the stomach by aid of the 

 acid ions.f Many changes are produced in the salts 

 contained by the sap of plants ; during these changes 

 free CO, OH, H, 0, C0 3 , N0 3 , S0 4 , P0 4 , C 2 4 , 

 C 2 H 3 2 , and other ions are constantly present from 

 the breaking down of organic or inorganic substances, 

 and the free ions assist in the transformation of carbo- 

 hydrates from one form to another. Fatty bodies 

 are abundant in many cells, especially in animal fat, 

 vegetables, seeds and fruit. They are formed by the 

 union of a fatty acid, such as oleic or palmitic acid 

 with glycerine, during which combination the fatty 

 acid replaces three hydroxyl ions split off from the 



* Abstracts, Jour. Chem. Soc., 1898, 714. 

 t Wroblewski: Zeit. fur Physiol. Chem., 1898, xxiv., 73. 



32 



