260 FRANKLIN P. MALL 



both ventricles as shown in fig. 15. The fibers from the conus 

 cross the anterior longitudinal sulcus and pass to the apex as 

 the bulbo-spiral band (fig. 6). Below these the fibers encircle 

 the right ventricle (fig. 1) and dip into the anterior longitudinal 

 sulcus as indicated in fig. 6. At the apex of the right ventricle 

 the fibers pierce the septum to pass into the left ventricle as shown 

 in fig. 12. 



At the base of the heart the fibers encircle largely the right 

 venous ostium (fig. 1) to reach the conus where they blend inti- 

 mately with the tendon of the conus (figs. 1, 3, 4, 8 and 13). At 

 this point we also recognize the circular band of the conus as 

 described by Ludwig, and subsequently by Krehl. This Mac- 

 Callum could not verify in the pig. However it is present but 

 by no means as marked as one would believe by reading Krehl 's 

 paper. It is seen in figs. 6 and 8 that a large loop encircles the 

 conus which is broken by a tendon, the superior aortic septum. 

 However, careful dissections of this region in man and in the pig 

 reveal a small circular band of fibers which encircles the conus 

 and is attached to the aortic septum only. So, as the aorta has 

 its own simple circular band which includes the left venous 

 ostium, there is a corresponding band in the right ventricle which 

 includes the conus only. This arrangement is fundamental and 

 may be described as the figure 8 of the base, one loop around the 

 conus and the other around the aorta and the left ostium, with 

 the cross piece as the septum aorticum. All the other loops of 

 muscle bands may be considered as modifications of the two loops 

 of the transverse figure 8, but they must all come back to the 

 cross piece of the 8, or aortic septum. One loop encircles the 

 main part of the bulbus and the other the main part of the sinus. 

 (See Schema B). 



The longitudinal bundles of the medial side of the right ven- 

 tricle connects with the papillary muscles of the left ventricle 

 and with the membranous septum on the right side of the heart 

 (figs. 3, 8 and 15). A portion of it passes over the front of the 

 heart to blend with the superficial bulbo-spiral band. This is 

 shown in fig. 13 and in fig. 15 where its attachment to the mem- 

 branous septum has been cut off, and in figs. 6 and 8 with the 



