LIST OF ILLUSTRATIONS XI 



KIG. PAG K 



69. Apparatus for Becording the Thickening of a Muscle at Two Points, 



for the purpose of studying the muscle wave .... 74 



70. The Thickening of a Muscle 75 



71. Method of Studying Polar Excitation of a Muscle .... 80 



72. Method of Arranging the Apparatus to Show Polarisation of Elec- 



trodes 82 



73. Several Models of Unpolarisable Electrodes (Waller) ... 83 



74. Simple Form of Unpolarisable Electrodes 83 



75. Plan of Apparatus for Studying the Changes of Excitability of 



Electrotonus 88 



76. Diagram Indicating the Changes of Excitability of a Nerve in 



Electrotonus 90 



77. To Illustrate the Principle of the Monochord .... 91 



78. A Second Form of Monochord 92 



79. The Eheochord as Arranged for Varying the Direction and 



Strength of a Current through a Nerve 92 



80. Arrangement of Apparatus for Studying the Velocity of a Nervous 



Impulse ............. 95 



81. Two Twitches of a Gastrocnemius when the Sciatic was Stimulated 95 



82. Anterior and Posterior Surfaces of the Frog's Heart ... 97 



83. Apparatus for Recording the Heart Beat by the Suspension Method 99 



84. Record of the Movements of the Frog's Heart by the Suspension 



Method 100 



85. Application of the First Stannius Ligature to the Frog's Heart 104 



86. Electrical Stimulation of the Ventricle of the Frog's Heart in 



Standstill by the Stannius Ligature to Show the ' Staircase ' 



Effect 106 



87. A Simple Form of Flexible Electrodes 106 



88. A Single Contraction of the Frog's Ventricle .... 107 



89. A Single Contraction of the Frog's Ventricle 108 



90. A Repetition of the Tracing of Fig. 89 with a Slower Movement 



of the Recording Surface 108 



91. The Effect of Two Successive Stimuli upon the Ventricle of the 



Frog's Heart 109 



92. Tetanisation of a Frog's Ventricle in Standstill by the Stannius 



Ligature 110 



93. Apparatus for Varying the Temperature of a Frog's Heart . . 112 

 94 a. Tracings Obtained by Immersing an Excised Frog's Heart in 



Diluted Blood at Different Temperatures . . . . . 114 

 94 b. Tracings Obtained by Immersing an Excised Frog's Heart in 



Diluted Blood at Different Temperatures . . . . .115 



95. Single Contractions of the Frog's Ventricle at Various Tempera- 



tures 117 



96. Diagram of the Variations of the Duration of a Single Ventricle 



Contraction at Different Temperatures 118 



97. Diagram of the Variations in Height of Contkaction of the Frog's 



Ventricle at Different Temperatures 118 



98. To Show the Course of the Vagus in the Frog .... 120 



99. The Course of the Sympathetic in the Frog 121 



