156 M. R. KING 



crus and forced up to the point of bifurcation of the two crura 

 and then down the left crus into the left ventricle (fig. 1). It 

 was found easy to fill the left crus in this manner but the complete 

 network on the ventricular walls could not be filled without two 

 to four more injections of about six cubic centimeters of inject- 

 ing fluid made at different points on the wall of the left ventricle. 



When the entire left portion of the S.V.S. was filled with the 

 injection fluid its distribution was found to be much more exten- 

 sive than can possibly be seen in a fresh heart or by dissections 

 (fig. 1). By employing Gerota's Prussian blue injection mass 

 even the very finest branches were made visible under the endo- 

 cardium. As has often been mentioned in previous descriptions 

 of the system, by far the greater part of it lies directly under 

 the endocardium. This is particularly of advantage in using the 

 injection method for the colored fluid which is distinctly visible 

 through the translucent connective tissue sheath, and the endo- 

 cardium affords a complete and accurate picture of the sub- 

 endocardial distribution of the system. 



As shown in figure 1, the distribution covers almost the entire 

 ventricular walls. The main two trabeculae come across the 

 left ventricle and are broken up into a network at the base of 

 the papillary muscles. This network does not reach to the 

 apices of the papillary muscles, however, but in nearly all cases 

 stops at a point midway between apex and base. Passing around 

 the papillary muscles the network extends under the cusps of 

 the bicuspid valve approaching very close to the fibrous ring of 

 the atrio-ventricular orifice. The network is not so complete 

 on the septal wall. There is a region about one and a half or 

 two centimeters in width around the base of the aortic orifice 

 and another about one centimeter in wddth which follows either 

 side of the crus as far as its point of branching, which contains 

 no superficial network. On the posterior ventricular wall the 

 network is found to be much more complete for only a single 

 bare area, scarcely one square centimeter in size, can be found. 



The left crus as it appears at its point of emergence from the 

 sub-aortic musculature, is very flat and superficial and remains 

 so until it reaches its point of branching where it sends branches 



