MUSCULAR ARCHITECTURE OF THE HUMAN HEART 227 



the septum aorticum superius; it consists chiefly of two layers of 

 elastic plates with connective tissue between them. (2) A region 

 between the aorta and the right ventricle or the septum aorticum 

 inferius; it consists of the elastic wall of the aorta, a thin layer of 

 the muscle of the conus and a layer of connective tissue. (3) 

 The region between the ventricles or the septum membranaceum.^^ 



Before considering the arrangement of the deeper layers of the 

 muscle bundles of the left ventricle it is necessary to describe 

 briefly a few of the peculiarities of the superficial bundles. These, 

 as has been stated, arise at the base and converge spirally toward 

 the apex; those over the right ventricle are in a more transverse 

 direction, while those over the left ventricle are more perpendicular 

 This is well shown in figs. 5 and 6, and has been well illustrated by 

 Wolff in his various papers. ^^ But in addition to the spiral fibers 

 which cross the anterior longitudinal sulcus quite transversely 

 there is often seen in the posterior longitudinal sulcus a bundle 

 which runs perpendicularly towards the apex and appears to be 

 better marked in the heart of the new-born child than in the adult. 

 This bundle is well pictured in Wolff's paper ^^ as well as in Henle's 

 Anatomy,^^ and as it is constant, it need not be considered a 

 variation but should be included in the description of the superfi- 

 cial bundles of the posterior side of the heart, which here have a 

 downward tendency often forming bundles as they approach the 

 apex." 



In addition to the bundle just described a small thin superficial 

 sheet is occasionally seen over the middle of the right ventricle 

 near the base of the heart. This is also better seen in the hearts of 



33 Figures illustrating the membranous septum may be found in His, I.e. ; Quain's 

 Anatomy, figs. 310 and 317; Toldt's Atlas, fig. 929; Spalteholz's Atlas, fig. 420; and 

 Piersol's Anatomy, fig. 660. 



'^ See also Bourgery, Traite Complet de I'Anatomie de I'Homme, Paris, 1836, 

 Tome 4, PI. 10; Bonamy, Broca et Beau, I.e., Tome 2, PI. 4; Quain's Anatomy, I.e., 

 vol. 2, fig. 320; Toldt's Atlas, I.e., figs. 929 and 930; Henle, I.e., vol. 3, fig. 39; as 

 well as elsewhere. 



35 Wolff, I.e., Tome2, Tab. 6. 



3« Henle, I.e., fig. 39. Also Toldt, fig. 930. 



3' Weber, I.e., p. 145, denies the existence of a fasciculus in the posterior longi- 

 tudinal sulcus. 



