288 SPECIAL HISTOLOGY. 



ventricle, where not unfrequently a distinct, second vortex 

 exists, in which case some of the superficial fibres arising 

 from the left ostium venosum also curve inwards in that vortex, 

 as they do in that of the left ventricle, and are continued into 

 the superficial fibres of the right ventricle, but, on account of 

 their intricate interlacement, cannot be traced further. Besides 

 these, other deeper fibres exist in the right ventricle, which 

 are disposed as follows : 1 . From the upper border of the septum, 

 and the left posterior side of the pulmonary opening, flattened 

 bundles commence and run in the septum, downwards and for- 

 wards, towards the apex of the heart and the anterior longitu- 

 dinal sulcus, where they join the superficial fibres, and are 

 continued with them into the vortex, whence they may be 

 traced as far as the anterior papillary muscle of the left ven- 

 tricle, (fig. 276 b, b ' , b"). 2. With these fibres are associated 

 others, running obliquely downwards and backwards, from the 

 right side of the pulmonary opening and the right portion of 

 the ostium venosum dextrum, beneath the superficial layer of 

 fibres on the free wall of the ventricle, as far as the posterior 

 longitudinal sulcus, where they curve abruptly towards the 

 septum, in which they accompany the fibres described under (1), 

 though more on the inferior half of the septum, to the apex of 

 the heart, and terminate in a similar way. 3. With these 

 fibres are also conjoined, to some extent, the elements of the 

 great papillary muscle of the right ventricle, whilst those of the 

 two smaller are continued into the fibres of the septum described 

 under (1). Besides this, all these muscles furnish direct fibres, 

 some of which descend from the ostium venosum and return 

 upon themselves, and some proceed from the network of the 

 trabecules earner and cannot be traced further. 



It would appear therefore, that the auricles, as regards their 

 muscular structure, are almost distinct ; whilst in the ventricles, 

 the entire superficial, tolerably thick muscular layer is continuous 

 all round, and is disposed as if the heart had only a single 

 cavity. Properly speaking, the left ventricle alone in this 

 respect, is independent, in which there is not only beneath the 

 superficial layer a very thick muscular mass arising and ending 

 in it, to which, also, the greater part of the septum belongs, but 

 which also receives nearly all the deeper muscular layers arising 

 on the right side, in the free wall of the ventricle, and inserted 



