Reaction velocities; enzymes as catalysts; general properties; extracellular and intracellular enzymes; chemical nature; nomenclature and classification; occurrence and preparation; general and individual enzymes; nature of enzyme action; accelerators and inhibitors; coenzymes and antienzymes; zymogens; physiological uses; further studies needed; references 181-201 CHAPTER XV--THE COLLOIDAL CONDITION "Colloids" and "crystalloids"; the colloidal condition a dispersion phenomenon; nomenclature and classification; conditions necessary to the formation of sols; gel-formation; general properties of colloidal solutions; suspensoids and emulsoids; adsorption; catalysis affected by the colloidal condition; industrial applications of colloidal phenomena; natural colloidal phenomena; references 202-220 CHAPTER XVI--THE PHYSICAL CHEMISTRY OF PROTOPLASM Heterogeneous structure of protoplasm; protoplasm a colloidal gel; water; salts; osmotic pressure; surface boundary phenomena; electrical phenomena; acidity and alkalinity; summary; vital phenomena as chemical and physical changes; references 221-238 CHAPTER XVII--HORMONES, AUXIMONES, VITAMINES, AND TOXINS External and internal stimulants; hormones; vitamines; auximones, toxins 239-248 CHAPTER XVIII--ADAPTATIONS General discussion; adaptations, accommodations, and adjustments; chromatic adaptations; morphological adaptations; accommodations; concluding statements 249-258 INDEX 259-268 INTRODUCTION