1 78 THE CONTRA CTION OF CARD I A C MUSCLE. 



ventricular ring, the ganglionic structures and the less modified muscular 

 tissue would be coterminous. 



If, then, the rhythmical power depends upon the presence of more 

 embryonic muscle, we ought to find those parts which we suppose to 

 contain such muscle especially rhythmical, quite independently of the 

 presence or absence of ganglion cells in them. We ought, in fact, to 

 find, according to our theory, that the bulbus arteriosus contracts 

 rhythmically with great ease, either spontaneously, or with such 

 slight constant stimulus as is implied by a steady distension of 

 its walls ; we ought to find that the muscular auriculo-ventricular 

 junction will respond to a stimulus with a series of contractions, and not 

 with a single contraction, as in the case of the auricular or ventricular 

 muscles proper — in this way, explaining incidentally the phenomenon of 

 the second Stannius ligature ; we ought to find that in the large veins, 

 even in those parts which are outside the region of ganglion cells, 

 spontaneous rhythmical contractions take place upon isolation. 



With respect to the bulbus, the experiments of Engelmann 1 in 1882 

 have shown most conclusively how easily this part, when isolated, will 

 beat rhythmically ; and the observations of Munk, 2 Lowit, 3 and others, 

 with respect to the presence of ganglion cells in the bulbus, have failed 

 to convince Engelmann that ganglion cells are really present there. 

 What Engelmann has observed for the bulbus arteriosus in the frog can 

 be still better seen in the conns arteriosus of the skate, where there is 

 a long stretch of circularly arranged muscular tissue, the merest touch 

 of any part of which is sufficient to start a regular rhythmical series of 

 contractions. 



Passing now to the remains of the canalis auricularis, the auriculo- 

 ventricular ring of muscle, we see that the second Stannius ligature, 

 or cut, not only stimulates this ring of tissue, but also the two Bidder's 

 ganglia as well, so that the rhythmical series of contractions which 

 results may be due to the stimulus affecting the special rhythmical 

 tissue of the ring, or directly stimulating the nerve cells of Bidder's 

 ganglia. The supporters of the motor ganglia theory of the heart's beat 

 have always attributed this rhythm to a stimulation of Bidder's ganglia, 

 and the latest supporter of this theory, viz. Kaiser, 4 asserts definitely 

 that, if Bidder's ganglia are removed, then ligature or section of the 

 auriculo-ventricular junction produces no special effect ; that, in fact, 

 each stimulus applied now produces only a single contraction, just as in 

 the case of the auricular or ventricular muscle, and not, as is always the 

 case before the removal of the ganglia, a series of contractions. It is 

 impossible to imagine a stronger piece of evidence that the rhythm is 

 dependent on motor ganglia than this — a particular part of the heart 

 always responds with a series of contractions to a single stimulus, but 

 upon removal of the ganglion cells gives only a single contraction to 

 a single stimulus. If this experiment is true, then most assuredly 

 the motor ganglia theory is put on a basis such as it never had before, 

 and, however improbable it may appear, must be taken into serious 

 consideration. 



Kaiser's argument is — Any stimulus applied here always gives a series of con- 

 tractions, not a single contraction ; this is due to the stimulus exciting a nerve 



1 Arch. f. cl. ges. Physiol., Bonn, 18S2, Bd. xxix. S. 425. 



" Arch. f. Physiol., Leipzig, 1878, S. 569. 3 Ibid., 1881, S. 399. 



4 Ztschr.f. Biol., Miinchen, 1894, Bd. xxx. S. 302. 



