THE SHEATH OF THE BUNDLE OF HIS 



67 



transition was observed. Such a transition could, perhaps, be 

 considered a means to offset the great numerical disproportion 

 which must exist between the fibers of the atrio-ventricular system 

 and the heart muscle fibers. 



Fig. 5 shows a camera lucida drawing from the auricular region 

 —the 'Knoten' — in a section of tissue from beef heart no. 12. 



Fig. 4 Camera lucida drawing; section of ventricular myocardium, beef heart. 

 A and B, Purkinje fasciculi; C, injection material within connective tissue sheath; 

 D, cardiac muscle fibers; E, fasciculus of heart muscle fibers in which fiber A ter- 

 minates. X 275. 



Point A shows the auricular muscle fibers cut in cross section. 

 From these, bundles of fibrillae pass off to enter a point of union 

 for many such fibril fasciculi, which place Tawara has called a 

 node. In this nodal point the fibrils are seen as confused strands 

 coursing in many different directions. The clear spaces G repre- 

 sent the indentations of the node which have been cut in the sec- 

 tioning, and within which the connective tissue nuclei can be 



