672 SPECIAL HISTOLOGY. 



and the greater part of those belonging to the right ventricle from the 

 posterior portion of the left ostium venosum. If the fibres of the left 

 ventricle are traced, it will be found, with the exception of those which 

 at the posterior longitudinal sulcus pass upon the right ventricle, that 

 they (Fig. 276 a, #', a") run towards the apex of the heart, and there 

 form the well-known vortex, and then curve inwards, forming loops ; and 

 are continued as the innermost, for the most part longitudinal, fibres of 

 the cavity of the ventricle, and either ascend as high as the venous 

 openings, or terminate in the posterior papillary muscle. Upon removal 

 of this set of fibres, a thick layer comes into view, interposed between 

 its external and internal portions, the fasciculi in which, at first sight, 

 appear to surround the cavity of the ventricle in an oblique and trans- 

 verse direction, although they seem to arise, without exception, from the 

 ostia venosa, and again to terminate in the same situation, and to de- 

 scribe a figure-of-8 turn, still more distinctly than the external muscular 

 layer, as has been clearly shown by Ludwig. I find that the bundles of 

 this layer (Fig. 276 c, c c" <?"'), after their origin from the left border 

 Fig. 276. of the aorta and the anterior half of the ostium 



venosum sinistrum, extend obliquely downwards, 

 and to the left (c), and then, before reaching the 

 apex of the heart, curve towards the posterior 

 wall of the ventricle (c'), whence they again as- 

 cend on the septum (c"} and the anterior wall 

 (c rfr \ and are finally inserted in the whole extent 

 of the venous opening, and also in the upper bor- 

 der of the septum (c ffff ). It is from these fibres 

 in the free wall of the ventricle that are derived 

 the deep layers which decussate with the superfi- 

 cial, and on the septum afford the fibres which, on the left side, run 

 obliquely from below and behind, upwards and forwards. 



On the right ventricle, there are much fewer independent fibres than 

 on the left. Most of the superficial fasciculi are continued upon the 

 left ventricle ; both the anterior, which are continued over the anterior 

 longitudinal sulcus and lost in the vortex, and also many of those which, 

 at the posterior longitudinal sulcus, stretch from the left to the right 

 ventricle. These latter fibres, consequently, completely encircle the 



FiG. 27G. Diagram of the left ventricle, with the septum, in order to show the course of 

 the muscular fibres, a a' a", superficial fibres : a, on the anterior wall ; a', the turning inwards 

 of them at the vortex; a", their passage into the posterior papillary muscle, b, b f , b", septal 

 fibres of the right side: b, their course, downwards and forwards; &', their passage into the 

 vortex and internal muscular layer of the left ventricle, as well as their termination in the 

 anterior papillary muscle, 6". c c"", middle muscular layer: c, commencement at the right 

 side of the ostium venosum, and course on the anterior wall obliquely downwards and back- 

 wards ; c 7 , curvature on the septum, and course on it, c" ; c" r , curvature on the anterior wall, 

 and deep course in it, to the end of the ostium venosum, <!"' '. 



