62 THE HEART 



to ventricle in the mammalian heart. But it does not necessarily 

 prove muscular conduction, since the bundle contains nerve fibres 

 and a few ganglion cells. Fredericq, however, states that he has 

 destroyed all the nerves in the bundle and its neighbourhood by 

 ammonia, but yet got no evidence of allorhythmia. He states 

 also that histological evidence shows that the nervous elements 

 of the bundle do not extend right through it. According to 

 Fredericq the mode of conduction in the bundle is undoubtedly 

 muscular. The opinion of Fredericq is weighty and all the more 

 interesting since formerly he held the neurogenic view. Even now 

 he holds that under certain conditions there is a nervous con- 

 duction in the heart. He bases his view upon the following experi* 

 ments. As long ago as 1886 he found that with feeble indirect 

 shocks he got these results : 



... ( Both ventricles stopped. 



Applied to one ventricle .-{,-, . , . j , 



( Both auricles continued beating. 



( Both auricles stopped. 

 Applied to one auric . -J fioth ventricles continued beating. 



He came to the conclusion, therefore, that there must be some 

 abnormality in the conduction in these cases, since ordinarily he 

 could obtain reciprocal conduction, whereas this mode of con- 

 duction affected both auricles and both ventricles, but did not 

 connect auricles to ventricles. More recently he found that if he 

 threw the heart into fibrillary contractions he obtained the same 

 results. The fibrillary contractions arising in one auricle pass 

 quickly to the other, but not to the ventricles ; similarly with the 

 ventricles, from ventricle to ventricle but not to the auricles. 



Fredericq thinks that fibrillary contractions pass quickly by 

 nervous means, and adduces the above experiments as evidence 

 that the A-V bundle contains no nerve fibres passing throughout 

 its course, since fibrillary contractions never pass from auricle to 

 ventricle. On the other hand, the rhythm of the ventricle is 

 normally that of the auricle, and is influenced whenever that of 

 the auricle is altered. Therefore the heart impulse passes by 

 muscular tissue and traverses the A-V bundle in its passage from 

 auricle to ventricle. The rate of conduction of the impulse along 

 the bundle is explained by the character of the muscle tissue of 

 which it is composed, since Fano has shown that the rate of con- 

 duction in cardiac muscle varies according to the stage of develop- 

 ment. It would therefore seem that the difference in structure 



