CONTENTS 



CHAPTER PAGE 



I. IRRITABILITY AS A SIGN OF LIFE i 



The Characteristics of Living Matter. Irritability. 

 Functional Changes as a Sign of Irritability. Functional 

 Changes in the Nerve Fiber. 



II. CHEMICAL SIGNS OF IRRITABILITY IN THE NERVE 

 FIBER . 10 



Signs of Metabolic Activities in a Tissue. Indirect Evi- 

 dence for Presence of Metabolic Activity in the Nerve 

 Fiber. Direct Evidence. Experimental Methods with Non- 

 Medullated Nerve Fiber. Medullated Nerve Fiber. Is 

 Carbon Dioxide Produced by Living Processes ? Discussion. 



III. CHEMICAL SIGNS OF IRRITABILITY IN THE NERVE 

 FIBER Continued 34 



Increased Metabolism on Stimulation. Experimental. 

 Electrical Stimulation. Other Stimulations. Discussion. 



IV. EXCITATION AND CONDUCTION 57 



Excitability and Metabolism. Degree of Excitability Com- 

 pared with Metabolism. Effects of Narcotics. Lower 

 Concentration. Higher Concentration. Direction of the 

 Nerve Impulse and Metabolic Gradient. Velocity of the 

 Nerve Impulse and Carbon Dioxide Production. 



V. CHEMICAL SIGNS OF LIFE 87 



Resting Metabolism in Seeds. Increased Metabolism in 

 Seeds on Injury. Other Tissues. A Chemical Sign of Life. 



VI. CONCLUSIONS 95 



Summary. Other Criteria of Life. Functions of Resting 

 Metabolism. Metabolism and Irritability. Chemical Con- 

 ditions in the Living Processes. Quantity of Life. 



APPENDIX. THE BIOMETER: How TO USE IT . . .109 



ix 



