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 Centfosome ..... 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 



