8o THE INVOLUNTARY NERVOUS SYSTEM 



Both Kuntz and Miss Abel agree with His junior that the 

 cardiac cells have come into the heart from outside, and both 

 trace them from cells belonging to the vagus which were at first 

 close against its root ganglia and afterwards have travelled out to 

 the heart. They both state that only vagus cells have thus 

 travelled into the heart. 



Do the cardiac nerve cells also supply motor nerves to any 

 muscle? Is there any evidence of two kinds of muscle in the 

 heart similar to the evidence I have given of two kinds of muscle 

 in the gut? There certainly is evidence, and it is of a most 

 striking kind. 



Fano in 1900 found that, when records were taken of the 

 contractions of the auricle and ventricle of the water tortoise, 

 Emys Europcea, a clamp being placed at the auriculo-ventricular 

 groove, the base line of the auricular tracing was not straight but 

 slowly undulating, the rhythm of the waves being often remark- 

 ably regular. The auricle of this tortoise shows the pres- 

 ence of two rhythmical activities going on simultaneously, the 

 one a tonic rhythm having the appearance of Traube-Hering 

 curves, and the other the ordinary heart beats superimposed on 

 this tonic rhythm. Fano at first looked upon this phenomenon 

 as indicating the presence of two kinds of muscle in the auricle, 

 the one the ordinary quickly contracting cardiac muscle and the 

 other a more slowly contracting kind, which in consequence of 

 the clamp in the auriculo-ventricular groove was set into rhythmic 

 action. He drew attention to the fact that atropine removed 

 these rhythmic tonic contractions while the heart beats con- 

 tinued, but muscarine removed the heart beats while the tonic 

 rhythm continued. Bottazzi found evidence of the same kind of 

 phenomenon in Amphibia, and in tortoises other than Emys Euro- 

 pcea, but always to a less extent than in Emys Europcea itself; and 

 Rosenzweig, working with Engelmann, found that the clamp at 

 the auriculo-ventricular groove was not necessary for the production 

 of this tonic rhythm, but that bloodlessness and a dying condition 

 of the heart were sufficient to bring about the phenomenon. 

 Thus, whereas in a freshly put up heart there might be no trace 

 of rhythmic tonic contractions, the same heart exhibited the 

 phenomenon strongly on the next day. Rosenzweig further ex- 

 amined the auricle of Emys Europcea histologically, and found 

 that close against the endothelium was a layer of muscular tissue 



