1909.] The Nerves of the Atrio-ventricular Bundle. 161 



(1) Numerous ganglion cells — monopolar, bipolar, and multipolar — whose 

 processes may pass — 



(a) To adjacent ganglion cells in the bundle ; 



(&) To the muscle fibres in the bundle ; 



(c) Through the muscle bundle so far as it was examined. 



(2) Abundant nerve fibres running through it in strands, the processes of 

 which may end (a) in ganglion cells in the bundle ; (b) in the muscle plexus, 

 or may pass through the part examined. 



(3) An intricate plexus of varicose fibrils around and in close relation to 

 the muscle fibres of the bundle. 



(4) An abundant vascular supply with well-marked vasomotor nerves and 

 sensory endings. 



II. Physiologically it has been shown that the atrio-ventricular band 

 constitutes the pathway which assures the communication of the atrio- 

 ventricular rhythm. When the bundle is sectioned or crushed the ventricles 

 cease momentarily to beat, though they soon regain pulsation, but with 

 a rhythm much more slow than that of the atrium. Pathological anatomy 

 supports this view ; the allorythmia or Stokes-Adams disease can be 

 explained satisfactorily by lesions involving this pathway. As a result of 

 these physiological experiments and from these pathological conditions, it has 

 been asserted that the contraction wave must be myogenic. To such 

 a deduction my anatomical findings are opposed. They demonstrate that in 

 these experiments and pathological conditions an important nerve pathway 

 is equally involved with the muscle bundle. Considering the neurogenic as 

 opposed to the myogenic hvpothesis from the anatomical standpoint, one 

 must acknowledge that the very complex nerve constituents of the bundle 

 indicate a a important nerve pathway and are very suggestive of an intricate 

 nerve mechanism. 



Can the atrio-ventricular bundle be regarded as a neuro-muscular spindle ? 



It has recently been stated that " the conclusion derived from the study of 

 the development and cytological structure of the conductive system is that it 

 is a neuro-muscular apparatus akin to the neuro-muscular spindle of voluntary 

 muscle" (Retzer (y)). Similar suggestions have been made by others, and 

 readily present themselves as a possible explanation of the position and 

 structure of the atrio-ventricular bundle. But have we anatomical data on 

 which to base such a conclusion ? To answer this it is necessary to consider 

 the structure of the neuro-muscular spindle. 



Were one to accept Golgi's definition, made in 1880, that it is " a bundle of 

 incompletely developed muscle fibres surrounded by a special sheath," one 



VOL. LXXXI. — B. M 



