256 FRANKLIN P. MALL 



muscles in the former than in the latter. Possibly this has been 

 the case on account of an abundance of pig's hearts. It is seen 

 by unrolling the left ventricle of the pig's heart that the chief 

 circular bands which arise from the bulbus fall into three distinct 

 bands which are easily separated from one another. The first 

 is the single circular band around the left ostium, and the second 

 and third are the spiral bands which enter the septum. The 

 superficial bulbo-spiral band instead of encircling the left ventri- 

 cle as it does in man divides into two bands (figs. 19 and 20) ; one 

 is attached to the anterior tendon of the aorta, BS, Post, while 

 the other encircles the anterior papillary muscle and is ultimately 

 attached to the posterior ligament of the aorta, BS, Ant, In doing 

 this the anterior superficial bulbo-spiral band, BS, Ant, passes 

 within the walls of the ventricle, between the anterior and the 

 posterior papillary muscles. In order to show this relation better 

 fig. 16 is given. In the specimen from which this figure was made 

 the left ventricle was cut open on its left side before the heart was 

 boiled in dilute acetic acid. Then the papillary muscles were 

 broken apart; the specimen shows clearly that the posterior 

 muscle sends its fibers over the right ventricle, and the fibers 

 from the anterior papillary muscles pass out of the apex of the 

 heart on the medial side of the right ventricle. The strand 

 marked x in fig 16 belongs to the anterior papillary muscle. Be- 

 tween the strands which enter the papillary muscles there is a 

 third which passes from the right ventricle to the left and blends 

 with the anterior bundle of the superficial bulbo-spiral band. By 

 this arrangement it is easily seen that the anterior papillary 

 muscle is intimately connected with the sino-spiral band and the 

 posterior partly with the bulbo-spiral butmostly with the muscle 

 bundles from the right ventricle both on its lateral and medial 

 sides. This arrangement is well shown in figs. 16 and 18. In 

 fig. 18 it is further seen that the roots of the posterior papillary 

 muscle not only reach outside of the heart through the bulbo- 

 spiral band to the aorta but also on the medial side of the right 

 ventricle through the longitudinal bundles of the right ventricle 

 to the membranous septum. On its posterior side it is intimately 

 attached to the circular bands by the way of a raphe which is not 



