216 FRANKLIN P. MALL 



bundles. This simple schema becomes distorted because the 

 \'-shaped loops are not limited to a relatively flat portion of the 

 ventricle wall but they encircle the whole ventricle and are also 

 ''tucked up" into the septum, especially at its anterior border. 

 The fasciculi and sheets which I shall describe are marked by their 

 points of origin, their ending, and especially by their relation 

 to the vortex of the left ventricle as well as by the muscular 

 septum of the ventricles. 



There is an agreement among authors regarding the course 

 of the muscular fibers on the external surface of the heart. How- 

 ever, it is well, in studying their course, to prepare several speci- 

 mens of adult hearts as well as those of children, in order to de- 

 termine variations in case they exist. This is best done by clean- 

 ing the muscle of the ventricles of hearts which have been well 

 fixed in carbolic acid or in alcohol, and by removing the atria 

 entirely. The superficial blcod vessels of the heart should be re- 

 moved also. By comparing a number of such specimens it will 

 easily be seen that in general the fibers over the right ventricle 

 are in a transverse direction and over the left in a perpendicular 

 direction. All this is clear when it is remembered that the apex 

 belongs entirely to the left ventricle and towards it most of the 

 muscle bundles stream to form the great vortex of the left ven- 

 tricle which surmounts the apex. Fibers on the right side must 

 cross both anterior and posterior longitudinal sulci to reach the 

 great vortex upon the apex, thus giving these a transverse di- 

 rection while those on the left side simply stream downward to 

 the apex. The transverse direction of the fibers over the right 

 ventricle is maintained somewhat more on the posterior sur- 

 face of the heart than on the anterior, because the posterior 

 fibers stream towards the small vortex of the right ventricle which 

 is higher up, while the anterior stream toward the great vortex 

 of the left ventricle which is lower down. What has been said 

 may be seen easily by superficial observation of any heart which 

 has had all of the epicardium removed. '^ 



1'' This is well shown in Mac(' nil urn's dinsram, fig. 15, which is reproducod in 

 Piersol's Anatomy, fig. 664. 



