1 04 THE INVOL UNTAR Y NER VO US S YSTEM 



that the lateral part near this was partly responsible, and that 

 the dorsal part, where the sinus extension joins the auriculo- 

 ventricular junction, had no part in the passage of the contrac- 

 tion to the ventricle, for when alone left, no contraction of the 

 ventricle took place. The small amount of tissue that could be 

 left near the aorta without interrupting the sequence was amazing. 

 The conclusion to which I came in 1888 was, that the muscular 

 tissue, along which the contractile wave passed to the ventricular 

 muscle, was especially situated at the ventral side near the aorta, 

 and was in connexion with the reticulated muscular tissue of the 

 auricles. At the same time I thought, as also did McWilliam, 

 that the more circularly arranged tissue in the sinus extension 

 might also, though at a slower rate, conduct a wave of contraction 

 right into the ventricle. 



Recently Laurens has taken up the re-examination of this 

 question in the tortoise and lizard. What I have called the 

 junction wall between the two auricles, and McWilliam the 

 sinus extension, he calls the sino-ventricular ligament or dorsal 

 ligament. He has repeated my experiments and found exactly 

 the same results. He describes the auriculo-ventricular junction 

 as shaped like a funnel and looks upon it, as I did, as the modi- 

 fication of the canalis auricularis. According to him there is no 

 muscular continuity from auricle to ventricle on the dorsal side, 

 but only on the ventral and lateral sides ; here, strands of 

 muscular tissue pass from the auricles directly into the ventricular 

 muscular tissue. Kiilbs and Lange have demonstrated the same 

 facts in amphibians, reptiles and birds, and in all cases have found 

 that this connecting musculature is more embryonic in character 

 than that of the auricles and ventricles. 



What was true of the cold-blooded heart I felt sure was true 

 of the warm-blooded, and I was much pleased when Stanley 

 Kent undertook to investigate the nature of the passage of the 

 contraction wave from auricle to ventricle in the mammalian 

 heart. He demonstrated that strands of muscular tissue did con- 

 nect auricle and ventricle together. His investigations were con- 

 firmed later by His junior, after whom these bundles of muscle 

 fibres are known in Germany, being called the bundle of His. The 

 most important investigation of the nature of this connexion was 

 made later in Aschoff s laboratory by Tawara, who showed that 

 the connecting strands were composed of a peculiar primitive 



