THE MEANING OF THE HEARTBEAT 179 



centre in the shape of Bidder's ganglia, because when that centre is removed 

 then only a single contraction takes place upon a single stimulus. It follows, 

 therefore, that if Bidder's ganglia and the muscular tissue of the auriculo- 

 ventricular ring be exposed, a stimulus to either ganglion ought to give a series 

 of contractions, while a stimulus to the auriculo-ventricular muscular ring 

 ought to give only a single contraction. 



It is possible to test this question in the following manner: — Slit up one 

 auricle and the ventricle, and pin back so as to expose the septum ; the two 

 vagi nerves on the septum, with their terminations in Bidder's ganglia, are then 

 most easily seen, as well as the muscular ring between auricles and ventricle, 

 and the whole field can be explored under a lens with the point of a 

 needle before and after removal of the septum and Bidder's ganglia. Now, cut 

 away the sinus, the whole preparation remains quiescent ; touch the outlying 

 auricular or ventricular tissue with the needle point, each time a single 

 contraction takes place, and no more ; touch either of Bidder's ganglia, not 

 a single contraction takes place ; pierce it again and again, and pull it about, 

 no sign of contraction. Touch the auriculo-ventricular ring of muscle with 

 the slightest stimulus, immediately a series of rhythmical contractions occurs. 

 It is most striking to see, after removal of the septum, how every portion 

 of auricular and ventricular tissue can be explored \x\> to the very edge of 

 the ring, without obtaining more than a single contraction, while immediately 

 the needle touches the muscular ring a series of rapid contractions results. 

 Conversely, the two Bidder's ganglia can be cut away, and yet stimulation 

 of the ring will produce a rhythmical result. In this latter experiment, 

 it is of course difficult to say whether all the cells have been removed ; 

 and it is this fact, that the certainty of having removed all the cells 

 of the ganglia carries with it the probability of nearly complete destruction 

 of the auriculo-ventricular ring, which renders Kaiser's experiment of doubtful 

 value. The exploration of the uninjured tissues by the fine point of the 

 needle is much more valuable, and appears to me conclusive against his view. 

 Unfortunately, the experiment, simple as it appears to be, is not always 

 successful, because it is not always possible to obtain standstill by the removal 

 of the sinus when the heart has been cut open. I performed the experiment 

 successfully many times during the winter months, but have hitherto failed to 

 obtain standstill during the spring months. Further investigation of 

 this crucial experiment is advisable. 



Finally, Engelmann, 1 in a recent paper, has shown that parts of the 

 large veins which continue to beat normally and spontaneously after 

 separation, which in fact are part of the normal rhythmical tissue from 

 which the heart-beat starts, are outside the region of ganglion cells, 

 and that, therefore, the spontaneous heart-beat starts from a non- 

 ganglionic region of muscular tissue. 



It still seems then, to me, that the explanation which I gave in 

 1883, of the reason why different parts of the heart differ in rhythmical 

 power — an explanation dependent upon morphological differences of the 

 muscular tissue and not upon the presence or absence of ganglion cells — 

 is right. Nothing that has since been written has tended to make 

 me alter that opinion. On the contrary, Engelmann 2 and W. His, 

 junior, 3 in their recent papers, have both come to the conclusion 

 that the varying rhythrnicity of different parts of the heart is due 

 to exactly the same morphological arrangement of the muscular 

 tissue as I had already pointed out. 



1 Arch./, d. ges. Physiol., Bonn, 1896, Bd. lxv. S. 109. 



"Ibid., 1897, Bd. lxv. S. 535. 



3 Arb. a. d. med. Klin, ztu Leipzig, 1893, Bd. i. S. 14-49. 



