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RUSKIN M. LHAMON 



Fig. 5 Camera lucida drawing; section from region of the 'Knoten,' showing a 

 large nodal point with connections. A, cardiac muscle fibers (auricular); B, 

 fibril strands from muscle fibers to the node; C, cross striations of fibril bundles 

 within the node; D, connective tissue; E, injection mass between connective tissue 

 and node; F, spaces produced by injection mass; G, indentation in node, showing 

 connective tissue within. 



seen. Cross striations of the fibril strands are plainly seen at 

 many points C. Surrounding these structures is the connective 

 tissue D which forms the sheath of the atrio-ventricular system 

 in this region, and which encloses the injection mass E within 

 it. Since uninfected specimens, do not show such a great separa- 

 tion between sheath and system, it seems probable that the 

 large spaces F were made by the injection and later fixation and 

 dehydration of the tissues kept them in the distended position 

 while the injection material settled to a small mass. 



There exists, then, in beef, calf and sheep hearts, a complete 

 connective tissue envelope applied to the sino-ventricular sys- 

 tem in all its ramifications. It clothes the system in its entirety 

 beginning above at the point where the main bundle takes its 

 origin and continues downward along the branching ventricular 

 fasciculi to their terminations. In the sub-endocardial region, 

 it is in relation with the sub-endocardial connective tissue, 

 while within the myocardium it is related to the interstitial myo- 



