THE CONTRACTION OF CARDIAC MUSCLE. 

 By AY. H. GASKELL. 



CONTENTS : The Meaning of the Heart-Beat, p. 169 The Sequence of the Con- 

 tractions of the different parts of the Heart, p. 180 The Causation of the 

 Beat of the Heart and of the Sequence of the Contractions of the Separate 

 Cavities is the same in Warm-blooded as in Cold-blooded Animals, p. 186 

 The Peculiarities of the Cardiac Muscle by which the Rhythm and Sequence 

 are to be explained, p. 188 On Fibrillar Contraction, p. 192 On the Tonicity 

 of the Cardiac Muscle, p. 194 The Meaning of the Ganglion Cells in the 

 Heart, and their Relation to the Cardiac Nerves, p. 197 The Nature of the 

 Action of the Cardiac Nerves (1) The Inhibitory Nerves, p. 203 ; (2) The 

 Augmentor Nerves, p. 216 ; (3) The After-action of the Inhibitory and 

 Augmentor Nerves, p. 219 The Action of Certain Poisons, 221 On the 

 Nutrition of the Heart, p. 224. 



THE MEANING OF THE HEART-BEAT. 



IN the early days of physiology, e.g. in the time of Haller, the beat of 

 the heart was supposed to be caused by the direct action of the blood as it 

 flowed through the cavities of the heart. It was soon, however, apparent 

 that the heart of such an animal as the frog could beat out of the body 

 when there was no blood flowing through it ; the heart-beat, conse- 

 quently, was clearly not due to the movement of the blood, but to some 

 peculiarity of the heart-tissue itself; it was therefore said that the 

 tissue of the heart possessed in itself automatic rhythmical power. Then 

 came the discovery of Eemak, 1 that groups of ganglion cells were present 

 in the sinus venosus of the frog's heart, with the subsequent discovery 

 of Bidder 2 of the two large masses of ganglion cells at the junction of 

 auricles and ventricle, and of Ludwig 3 of the ganglion cells in the inter- 

 auricular septum. At this period the automatic rhythm of respiration 

 was ascribed to the action of groups of nerve cells in the respiratory 

 centre, so that it was natural, indeed inevitable, that a similar mechanism 

 should be assumed to explain the automatic cardiac rhythm. Hence 

 arose the conception that Kemak's ganglia in the sinus venosus acted the 

 part of an automatic rhythmical centre, sending out impulses to the cardiac 

 muscular tissue at regular intervals, and so caused the beat of the heart. 

 This view received apparently its confirmation and its proof 

 by the well-known experiments of Stannius, 4 which, according to 

 Eosenthal, 5 were to be explained on the same principles as he had 

 already laid down for the respiratory centre. 



1 Arch.f. Anat., PhysioL u. wissensch. Med., 1848, S. 139. 



2 Bidder and Rosenberger, ibid., 1852, S. 172. 



3 Ibid., 1848, S. 139. 4 Ibid., 1852, S. 85. 



5 " Bemerkungen ueber die Thatigkeit der automat. Nervencentra insbesondere ueber 

 die Athembewegungen," Erlangen, 1875. 



