Viii CONTENTS 



Chapter 4 



CELL METABOLISM 64 



19. Chemical Reactions 64 



20. Enzymes 66 



21. Factors Affecting Enzyme Activity 69 



22. Respiration and Cellular Energy 71 



23. The Dynamic State of Protoplasm 74 



24. Special Types of Metabolism 75 



Chapter 5 



PRINCIPLES OF PHYSIOLOGY 78 



25. Types of Nutrition 78 



26. Ingestion, Digestion and Absorption 79 



27. Circulation 84 



28. Respiration 87 



29. The Elimination of \Vastes Other than 



Carbon Dioxide 92 



30. Protection 95 



31. Motion 98 



32. Irritability and Response 103 



Chapter 6 



REPRODUCTION 114 



33. Asexual Reproduction 115 



34. Sexual Reproduction 116 



35. Reproductive Systems 122 



36. Fertilization 123 



37. Embryonic Development 126 



38. Protection of the Embryo 131 



39. The Control of Development 133 



Part II. The Animal Kingdom 



Chapter 7 



THE PRINCIPLES OF TAXONOMY 139 



40. The Science of Taxonomy 139 



41. The Binomial System 140 



42. Higher Categories 141 



43. Uses of Taxonomy 141 



