224 FRANKLIN P. MALL 



of the left ventricle as a basket, or better as a cylinder, for it is 

 open at both ends, was first emphasized by Krehl, and just this 

 point is what has caused so much difficulty in our laboratory, 

 for according to MacCallum the cylinder easily resolves itself 

 into a single sheet or scroll in the foetal pig as well as in the adult 

 heart. To explain this apparent contradiction is one of the ob- 

 jects of this communication. Before taking up this main point 

 it will be necessary to consider briefly the arrangement of the 

 muscle fibers at the base of the heart, at the apex, the membra- 

 nous septum and, incidentally, the atrio-ventricular bundle. 



Fig. 2 is given to show the arrangement of the superficial 

 bundles at the apex of the heart, which shows a vortex under each 

 ventricle. A satisfactory analysis of the vortex of the left ven- 

 tricle, showing its two horns, is given by Pettigrew.^^ He show- 

 ed that it is easy to separate the two bundles of muscle entering 

 the apex, into anterior and posterior horns, as Haller did, and 

 judging by his illustration, one passes to the septum and the 

 other to the interior of the left ventricle. This I have been able 

 to confirm fully in numerous specimens of human hearts. It 

 is not so easily confirmed in the pig's heart. 



An excellent illustration of the arrangement of the muscle fibers 

 at the base of the heart is given by Bonamy, Broca and Beau.-^ 

 My fig. 1 differs from theirs inasmuch as it includes the tendinous 

 connection between the pulmonary artery and the aorta with the 

 fibers arising from it. Also on the posterior side I show the fibers 

 coming out of the septum and passing under those that arise 

 from the left fibrous ring ; these two sheets are pictured as a single 

 sheet in their figure. 



Since the chief muscle bundles of the heart are connected either 

 directly or indirectly with the fibrous bands at its base it is neces- 

 sary to have a clear understanding of them. These include the 

 membranous septum of the ventricles, which is continued into the 

 aortic septum. E. H. Weber made it clear that the architecture 



" Pettigrew, Phil. Trans. London, 1864. This figure is copied in Quain'.s 

 Anatomy, Tenth Edition, 1892, vol. 2, Fig. 322. 



" Bonamy, Broca and Beau, Atlas d' Anatomic descriptive, Paris, gives an 

 excellent illustration of the apex of the human heart. Toldt (Atlas, Berlin und 

 Wien, 1901, Fig. 931) also gives a satisfactory figure. 



