PLATE 2 
EXPLANATION OF FIGURES 
3 External bundles of the right atrium of the dog heart, viewed from the 
right side. In this heart the ‘concentration area’ of T. Lewis was strikingly 
developed. An unusual bundle extends onto the right surface of the superior 
vena cava. 
4 External bundles of the left atrium of a human heart, viewed from the left 
side. The visceral pericardium and the coronary vessels have been removed. 
The left atrial appendage is opened along its margin to show the intermediate 
group of pectinate muscles. 
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