THE SINO-VENTRICULAR SYSTEM 161 



in contrast with the rough edges in other parts of the bone. 

 However, since many of the bones develop into very irregular 

 and abnormal shapes it is impossible to determine any constant 

 relations of the Knoten and crus commune to it. 



The character of the branching of the system throughout both 

 ventricles was quite constant and characteristic in certain regions 

 (fig. 7). The mode of branching may be classified under four 

 heads: 1) A scroll-like branching especially pronounced on the 

 anterior wall of the right ventricle where the right crus, in 

 branching at the base of the anterior papillary muscle, sends a 

 main branch up to the conus. This branch assumes a gentle 

 curvelike course. 2) A very coarse network, the meshes of 

 which are composed of numerous fine faciculi or of single fasciculi 

 which are very flat and wide (fig. 12). This form is always 

 found on the right septal wall and is especially pronounced at 

 the base of the posterior papilla. Intermingled with the coarse 

 network there is always present an anastomoses of fine fasciculi 

 which make up a finer network. 3) In the termination of the 

 branching on the ventricular wall around the bicuspid and tri- 

 cuspid orifices instead of a network or scroll there is found a 

 termination of the branches into fine filaments. This is prob- 

 ably the most pronounced of the four types or arrangements and 

 is generally free from intrusion of the other types. 4) A fine 

 network made up almost entirely of single fasciculi. This type 

 is especially evident in the apices of both ventricles but is'found 

 to a greater or less extent in all parts of the ventricles. 



In many places one is not able to say which form of branch- 

 ing predominates since there exists an intermixture of all forms. 

 Nor in any one place is it possible to get one type entirely exempt 

 from all of the other three because of the gradual transition of 

 one form into another. Nevertheless, the point to be empha- 

 sized is that there exist in certain places in the beef heart, cer- 

 tain predominating characteristics of branching. These charac- 

 teristics of branching seem to be determined in all cases by the 

 arrangement of the trabeculae carnae within the ventricle of the 

 heart on which they lie. The different characters of trabeculae 

 carnae in different parts of the heart are v^ery constant and fall 



