236 FRANKLIN P. MALL 



left ventricle it is not so easy to convince one's self regarding a 

 constant arrangement. Furthermore, it is difficult to describe the 

 arrangement of the muscle bundles clearly, which in turn makes 

 the literature difficult to understand. 



The immediate connections of the two horns of the vortex of the 

 left ventricle can be given with precision and in order to make 

 them clear I have had a number of figures (5 to 12), drawn from 

 the same heart. The views given in figs. 2, 3 and 4 have been omit- 

 ted but in general they correspond so closely with them that it, 

 is unnecessary. In figs. 5, 6 and 7 the superficial muscle bundles 

 which form the superficial bulbo-spiral band which enters the apex 

 of the heart through the posterior horn of the vortex are drawn 

 with a smooth surface and the several bundles in different draw- 

 ings are marked with the same letters, A , B and C, in order that it 

 is possible to identify them in the different figures. The most 

 posterior sheet, that which arises from the tendinous ring around 

 the left venous ostium, is marked A, that which arises from the 

 side of the aorta, B, and that which arises from the septum aor- 

 ticum (or the conus) C. Those marked D and E belong to the 

 superficial sino-spiral band and enter the anterior horn of the 

 vortex. It is seen by comparing figs. 2 and 7 that the apex is 

 formed entirely by the anterior horn of the vortex and that the 

 posterior horn encircles the apex. This is shown in an exagger- 

 ated way in MacCallum's account of the foetal pig's heart. ^'^ The 

 locking of the two horns of the vortex is shown at C and D in fig. 7. 

 Here they are blended completely but they may easily be separ- 

 ated by running a probe into the left ventricle. Specimens made 

 in this way show a general tendency of all of the fibers of one horn 

 to run at right angles to those of the other. The bundle marked 

 C arises from the septum aorticum superior •'^■* which is much more 

 pronounced in the dog and pig than in man. The line drawn on 

 this bundle in fig. 6, X, shows the position of the cut surface, X 

 in fig. 8. 



*^ MacCallum, I.e., fig. 16. Also in Piersol's Anatomy, fig. 665 and in Morris- 

 McMurrich's Anatomy, fig. 383. Most of MacCallum's figures are reproduced in 

 the latter work. 



^* Tendon of the conus, MacCallum; tendinous band between the pulmonary ar- 

 tery and aorta, Krehl. 



