MUSCULAR ARCHITECTURE OF THE HUMAN HEART 217 



All of the superficial fibers may be described as arising around 

 the tendinous rings at the base of the heart to which the valves 

 are also attached. However, these rings are intimately related 

 to the aorta and pulmonary artery through the membranous 

 septum, which marks the inter-ventricular opening in the embryo. 

 In fact it may be considered to represent much more than this, 

 for it extends upward to include the aorta and pulmonary artery, 

 the tendon between these having been well described by Krehl. 

 The tendinous rings inclose both atrio-ventricular openings and 

 extend to include the membranes which close the openings be- 

 tween the right and left hearts in the embryo. The extent of 

 this tendinous band is well shown in fig.l, in which the inter- 

 ventricular membrane is marked X and its extension to the 

 pulmonary artery X' . It is further seen that the course of the 

 muscle fibers from these tendons is not uniform in all directions 

 showing marked differences in each portion of the heart. The 

 fibers from the left side of the heart. A, pass downward towards 

 the apex, those around the right side, B', B" , are transverse, 

 while those around the pulmonary artery. A' , are circular. Those 

 marked A pass directly to the great vortex forming its poster- 

 ior horn^^ (fig. 2, A,) while those marked B cross the pos- 

 terior longitudinal sulcus to the vortex of the right ventricle 

 and finally across the anterior longitudinal sulcus to the anter- 

 ior horn of the great vortex, (fig. 2, B). 



In general, then, the superficial fibers of the wall arise from the 

 tendinous structures at its base and converge toward the apex 

 to form the great vortex of the left ventricle. Those arising 

 from the conus, the left side of the aorta and the left side of the 

 left ring,( fig. 1, A, A' ), pass to the posterior horn of the vortex, 

 and ultimately to the septum, while those arising mostly from the 

 right fibrous ring posteriorly, (fig. 1, B, BO,pass around to the an- 

 terior side of the heart to form the anterior horn of the vortex, 



1^ In Haller's Physiology, London, 1764, vol. 1, p. 7.5, we find the vortex described 

 as being composed of two horns to correspond with the two main bands of muscle 

 which penetrate the heart here. According to Haller one group is inserted into the 

 septum and the other penetrates the left ventricle and returns in a contrary direc- 

 tion to the base. This is substantially correct. 



