CONTENTS 



CHAPTER PAGE 



I Our Approach 1 



An Open and Unbiased Mind Is Necessary — The Growth 

 of Knowledge — The Thoroughness of Biological Research 

 — The First Appearance of Living Things — Preservations 

 in Rocks — Where and How Living Matter Originated — 

 Protoplasm Is Life — Lower and Higher Organisms — All 

 Living Things Composed of Cells — Growth of Knowledge 

 of Microscopic Organisms — Over a Hundred Thousand 

 Species of Microscopic Forms 



II Filterable Viruses 14 



Too Minute for the Most Powerful Lenses — Their 

 Activities 



III Bacteria 16 



Neither Animals Nor Plants — The Multiplication of Bac- 

 teria — Mass Action of Bacteria — Helpful Bacteria — 

 Man's Control of Bacteria 



IV Spirochaetes 23 



Forms Closely Related to Bacteria — Their Importance — 

 Types and Species — Cause Disease in Man and Beast — 

 The Spread of Spirochaete Diseases 



V The Fundamental, Living Substance — Protoplasm ... 31 



Difficult to Comprehend — A Typical Cell — The Nature of 

 Protoplasm — Organization — Vitality — Encystment and 

 the Fundamental Organization — Individuality Unchanged 

 by Encystment — Derived Organization — Irritability and 

 Adaptation — Biological Classification 



VI The Borderline Between Plants and Animals 42 



The Two Criteria — Arbitrary Decisions Necessary — The 

 Mystery of Chlorophyll — Clarity in Classification Needed 



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