252 FRANKLIN P. MALL 



the superficial band on the dorsal side of the aorta. The small 

 circular band ends in the posterior triangular field. The sino- 

 spiral bundle encircles the right ventricle and blends with the 

 longitudinal band of the right ventricle to form the anterior horn 

 of the vortex before entering the left ventricle. Here they end 

 partly in the papillary muscles. Other single loops encircle the 

 conus and are attached to the aortic septum, or tendon of the 

 conus. 



While most anatomists state that all of the muscle bundles of 

 the left ventricle form loops or V-shaped bundles which are 

 attached to tendons at the base of the heart, this has been denied 

 from time to time. Occasionally I have also found a bundle which 

 seems to turn upon itself at the base of the heart as shown in fig. 

 14. It is noticed in this figure that a large bundle lies midway 

 between the superficial bulbo-spiral and the deep bulbo-spiral band, 

 passes diagonally through the septum to the base and then turns 

 downward. It then encircles the base, blends with the deep bulbo- 

 spiral band and ends at the dorsal side of the aorta in its posterior 

 ligament. No such bundle is seen in figs. 8 nor 13. But it is quite 

 easy by comparing figs. 8 and 10 to imagine a portion of the super- 

 ficial bulbo-spiral band separated during part of its course to form 

 the variation seen in fig. 14. Beside this one example I have not 

 found any bundles which might be considered as forming V- 

 shaped loops pointing away from the apex and towards the base 

 in the left ventricle. But since the loops entering through the 

 apex, as well as the main circular bands, pass nearly twice around 

 the heart before they end, many variations must occur, and by a 

 stretch of the imagination they may be found in every specimen. 



The two muscle strands which cover almost the entire exterior 

 of the heart and enter at the vortex are finally distributed over the 

 interior of the left ventricle as well as to the papillary muscles. 

 All ultimately end at the atrio-ventricular ring. A complete 

 separation of these bands under the endocardium as they are 

 separated under the epicardium is hardly possible. However, 

 with some reserve a statement may be made regarding their 

 distribution within the left ventricle. 



