10 CONTENTS. 



PAGE 



D. The Causes of the Pressure in the Arteries, Capillaries, and Veins ... 91 

 Balance of the factors producing arterial pressure, 92 — The arterial pulse, 93 — The 



capillary pressure and its cause, 93- Extinction of tile arterial pulse in the capillaries, 

 94 — Venous pressure and its causes, 94— Subsidiary forces assisting the blood-flow, 95 — 

 Respiratory pulse in the veins, 96 — The dangerous region, entrance of air into veins, 97. 



E. The Velocity of the Blood in Arteries, Capillaries, and Veins 98 



Measurement of velocity in large vessels. Stromuhr, 98 — Measurement of rapid 



changes in velocity, Kin — Velocity and pressure of blood compared, KM — Relation of 

 velocity to the sectional area of the vascular bed, 102 — Time spent by blood in 

 capillary, 103. 



F. The Blood-flow through the Linus 103 



(}. The Pulse Volume and the Work Done by the Ventricles 104 



The cardiac cycle, 104 — The pulse volume, 105 — The work of the ventricles, 106 — 

 Heart's contraction as a source of heat, 108. 

 II. The Mechanism of the Valves of the Heart 108 



I'se of the valves. 108 — The auriculoventricular valves, 108 — Use of the tendinous 

 cords, 109 — The papillary muscles and their uses, 110 — The semilunar valves, 110 — 

 Lunuhe and corpora arantii, 111. 

 I. The Changes in Form and Position of the Beating Heart, and the Cardiac 



Impulse 112 



General changes in the heart and arteries, 112 — The heart and vessels in the open 

 chest, 113 — Changes of size and form in the beating ventricles, 113 — Changes of posi- 

 tion of the ventricle, 114 — Changes in the auricle, great veins, and great arteries, 115 

 — Effects of opening the chest, 115 — Probable changes in heart in the unopened chest, 

 116 — The cardiac impulse or apex beat, 117. 



J. The Sounds of the Heart 118 



Relations and character of the heart-sounds, 118 — Cause of the second sound, 118 — 

 Causes of the first sound, 119. 



K. The Frequency of the Cardiac Cycles 121 



L. The Relations in Time of the Main Events of the Cardiac Cycle .... 121 

 The auricular, ventricular, and cardiac cycles, 122 — The variability of each cycle, 

 123 — Relative lengths of ventricular systole and diastole, 123 — Lengths of auricular 

 systole and heart pause, 124. 



M. The Pressure Within the Ventricles 125 



Range of pressure within ventricles, 125 — Methods of recording ventricular press- 

 ures. 126 — General character of curve of intraventricular pressure, 128 — Effect of 

 auricular systole on the curve of ventricular pressure. 130— The opening and closing 

 of the heart valves in relation to the curve of ventricular pressure, 130— Analysis of 

 the curve of ventricular pressure, 133 — Negative pressure within the ventricles, 134. 



N. The Functions of the Auricles 135 



The auricle as a force pump. 135 — Time relations of auricular systole and diastole, 

 136 — Statement of functions of auricles, l.;i; Negative pressure within the auricles, 

 137— Is the auricle emptied by its systole? 138— Question of regurgitation from auri- 

 cles to veins, 138. 



O. The Arterial Pulse 139 



Nature and importance of the arterial pulse, 139— Rate of transmission of the pulse- 

 wave, 1 1(1 Frequency and regularity of the pulse, 141 — Arterial tension as indicated 

 by the pulse, 141— Size and celerity of pulse. 1 II The pulse-trace, or sphygmogram. 

 142— Analysis of the sphygmogram, 143— The dicrotic wave, 143— The diagnostic use 

 of i lie sphygmogram. 115. 



Part II.— The [nnervation ok the Heart (By W. T. Porter) 148 



The cause of the rhythmic heart-heat. IIS The intracardiac ganglion ells and 

 nerves, 148— The nerve theory of the heart-beat, 149— The muscular theory of the 

 heart-beat, 150 The excitation wave and its passage over the heart, 152 The passage 

 of the excitation wave from auricle to ventricle, 154— The refractory period and com- 

 pensatory pause, 156, 

 A. The Cardiac Nerves 159 



Anatomical arrangement of the heart nerves, 159 The inhibitory nerves. 161 — 

 Effect of inhibition on the ventricles 162— Effect of inhibition on the auricle and 

 sinus, L64 Effect of inhibition on the bulbus arteriosus, 165 Effect of inhibition on 

 the irritability of the heart. 165 Relation of inhibition to rate and strength of stim- 

 ulus, 165 -Arrest of the heart in systole, 165— Comparative inhibitory power of the 

 two vagi. 166 Effect of the septal nerves on the inhibition, 166— Theories of the 

 nature of vagus inhibition, L66 Relation of age, temperature, and intracardiac press- 

 are to inhibition, 167 — The augmentor or accelerator nerves of the heart, 167 — Effect 

 of stimulating the augmentor nerves, Kill Simultaneous stimulation of the accelerator 

 and inhibitory fibres, 17<» classification of the inhibitory and augmentor fibres, 171 — 

 The centripetal nerves of the heart. 172 Existence of sensory nerves in the heart, 



