xii CONTENTS 



CHAPTER PAGE 



Fate of Foods in Higher Animals . .... 61 



Role of Oxygen in Metabolism . . . . , 62 



Aerobic and Anaerobic Forms ..... 63 



Combustion and Respiration . . . . .64 



Poisons and Antiseptics 66 



Cycle of the Elements in Organic Nature ... 68 



The Nitrogen Cycle 71 



Destruction of Organisms 72 



Putrefactive Organisms . ... 73 



Denitrification and Nitrogen Fixation ... 75 



Nature of Energy Transformed 77 



Movement 77 



Heat 79 



Electricity 79 



Light . . .80 



Enzymes and Enzymatic Action .... 82 



Internal Secretions and Hormones .... 86 



IV. GROWTH 90 



Cumulative Integration 91 



Amitosis and Mitosis . 92 



Abnormal Mitosis 97 



Nature of the Centrosome 98 



Influence of External Conditions on Growth . . . 100 



Light and Heat 101 



Chemical Agents 102 



V. TISSUE DIFFERENTIATION FOR SPECIFIC FUNCTIONS . . 104 



Differentiation in Animals .... .104 



Alimentary System 104 



Sensory Organs, Cephalization .... 107 

 Skeletal Structures . . . . . . .110 



Endoskeleton 110 



Exoskeleton 112 



Muscular System . . . . . . .113 



Circulatory System . .' . . . . .114 



Excretory Organs . 117 



Differentiation in Plants 121 



Plant Movement 123 



