CONTENTS. xi 



SECTION III. 



THE NATURE OF THE CHANGES THROUGH WHICH AN ELECTRIC CURRENT 

 IS ABLE TO GENERATE A NERVOUS IMPULSE. 



Action of the Constant Current. 



PAGE 



74. Action of the constant current ; making and breaking contractions . 128 

 75. Electrotonus. Effect of the constant current on the irritability of 



the nerve. Katelectrotonus. Anelectrotonus .... 130 



76. Electrotonic currents 132 



77. Relation of electrotonus to nervous impulses, and to the effects of 



the constant current 134 



S 78. Action of the constant current on muscle 136 



SECTION IV. 

 THE MUSCLE-NERVE PREPARATION AS A MACHINE. 



79. The influence of the nature and mode of application of the stimulus 

 on the magnitude of the contraction. Maximal and minimal 

 stimuli. Influence of abruptness and duration of stimulus. 

 Some parts of a nerve more irritable than others . . . 138 



80. Frequency of repetition necessary to produce tetanus; pale and red 



muscles. The muscular sound 141 



81. The influence of the load; effect of resistance. The work done ' . 143 



82. The influence of the size and form of the muscle .... 144 



SECTION V. 



THE CIRCUMSTANCES WHICH DETERMINE THE DEGREE OF IRRITABILITY 

 OF MUSCLES AND NERVES. 



83. Diminution and disappearance of irritability after severance from the 

 body. Effect of division of nerves ; degeneration of nerve fibres. 



Eegeneration 145 



84. The influence of temperature 148 



85. The influence of blood supply 149 



86. The influence of functional activity. Exercise. Fatigue. , The causes 



of exhaustion 150 



SECTION VI. 



THE ENERGY OF MUSCLE AND NERVE AND THE NATURE OF MUSCULAR 

 AND NERVOUS ACTION. 



87. Nature of the act of contraction and the act of relaxation. The 

 relation of the energy of work to the energy of heat. The relation 

 of nitrogenous metabolism to the energy of contraction . . 153 



88. The nature of a nervous impulse . . . . . . 156 



